Physics M.C.Q (1 Marks)

Curie temperature is the temperature above which(a) A paramagnetic material becomes ferromagnetic(b) A ferromagnetic material becomes paramagnetic(c) A paramagnetic material becomes diamagnetic(d) A ferromagnetic material becomes diamagnetic

Two short magnets placed along the same axis with their like poles facing each other repel each other with a force which varies inversely as(a) Square of the distance(b) Cube of the distance(c) Distance(d) Fourth power of the distance

The magnetic moment of atomic neon is(a) Zero  (b) μB/2(c) μB(d) 3μB/2

Demagnetisation of magnets can be done by(a) Rough handling(b) Heating(c) Magnetising in the opposite direction(d) All the above

A ferromagnetic material is heated above its curie temperature. Which one is a correct statement(a) Ferromagnetic domains are perfectly arranged(b) Ferromagnetic domains becomes random(c) Ferromagnetic domains are not influenced(d) Ferromagnetic material changes itself into diamagnetic material

If a diamagnetic substance is brought near north or south pole of a bar magnet, it is(a) Attracted by the poles(b) Repelled by the poles(c) Repelled by the north pole and attracted by the south pole  (d) Attracted by the north pole and repelled by the south pole

The material of permanent magnet has(a) High retentivity, low coercivity(b) Low retentivity, high coercivity(c) Low retentivity, low coercivity(d) High retentivity, high coercivity

The permanent magnet is made from which one of the following substances(a) Diamagnetic(b) Paramagnetic(c) Ferromagnetic(d) Electromagnetic

Temperature above which a ferromagnetic substance becomes paramagnetic is called(a) Critical temperature(b) Boyle's temperature(c) Debye's temperature(d)  Curie temperature

The number of turns and radius of cross-section of the coil of a tangent galvanometer are doubled. The reduction factor K will be (a) K (b) 2K(c) 4K     (d) K/4

The bob of a simple pendulum is replaced by a magnet. The oscillations are set along the length of the magnet. A copper coil is added so that one pole of the magnet passes in and out of the coil. The coil is short-circuited. Then which one of the following happens(a) Period decreases(b) Period does not change(c) Oscillations are damped(d) Amplitude increases

Twists of suspension fibre should be removed in vibration magnetometer so that(a) Time period be less(b) Time period be more(c) Magnet may vibrate freely (d) Cannot be said with certainty

The time period of a freely suspended magnet is 4 seconds. If it is broken in length into two equal parts and one part is suspended in the same way, then its time period will be(a) 4 sec (b) 2 sec(c) 0.5 sec(d) 0.25 sec

A magnetic needle suspended horizontally by an unspun silk fibre, oscillates in the horizontal plane because of the restoring force originating mainly from(a) The torsion of the silk fibre(b) The force of gravity(c) The horizontal component of earth's magnetic field(d) All the above factors

Two magnets are held together in a vibration magnetometer and are allowed to oscillate in the earth's magnetic field with like poles together, 12 oscillations per minute are made but for unlike poles together only 4 oscillations per minute are executed. The ratio of their magnetic moments is(a) 3 : 1   (b) 1 : 3(c) 3 : 5    (d) 5 : 4

The time period of oscillation of a freely suspended bar magnet with usual notations is given by

Vibration magnetometer before use, should be set(a) In magnetic meridian(b) In geographical meridian(c) Perpendicular to magnetic meridian(d) In any position

The period of oscillation of a magnet in vibration magnetometer is 2 sec. The period of oscillation of a magnet whose magnetic moment is four times that of the first magnet is(a) 1 sec(b) 4 sec(c) 8 sec  (d) 0.5 sec

Two magnets of same size and mass make respectively 10 and 15 oscillations per minute at certain place. The ratio of their magnetic moments is(a) 4 : 9(b) 9 : 4(c) 2 : 3    (d) 3 : 2

Time period of a freely suspended magnet does not depend upon(a) Length of the magnet(b) Pole strength of the magnet(c) Horizontal component of earth's magnetic field(d) Length of the suspension thread

In sum and difference method in vibration magnetometer, the time period is more if(a) Similar poles of both magnets are on same sides(b) Opposite poles of both magnets are on same sides(c) Both magnets are perpendicular to each other(d) Nothing can be said

Due to the earth's magnetic field, charged cosmic ray particles(a) Require greater kinetic energy to reach the equator than the poles(b) Require less kinetic energy to reach the equator than the poles(c) Can never reach the equator(d) Can never reach the poles

The angle between the earth's magnetic and the earth's geographical axes is(a) Zero(b) 17°(c) 23°(d) None of these

The period of oscillation of a vibration magnetometer depends on which of the following factors(a) I and M only(b) M and H only(c) I and H only(d) I, M and H only

At a place, the horizontal and vertical intensities of earth's magnetic field is 0.30 Gauss and 0.173 Gauss respectively. The angle of dip at this place is(a) 30°(b) 90°(c) 60°(d) 45°

Which of the following is most suitable for the core of electromagnets(a) Soft iron(b) Steel(c) Copper-nickel alloy(d) Air

Force between two unit pole strength placed at a distance of one metre is

To measure which of the following, is a tangent galvanometer used(a) Charge(b) Angle(c) Current(d) Magnetic intensity

The time period of a bar magnet suspended horizontally in the earth's magnetic field and allowed to oscillate(a) Is directly proportional to the square root of its mass(b) Is directly proportional to its pole strength(c) Is inversely proportional to its magnetic moment(d) Decreases if the length increases but pole strength remains same

Lines which represent places of constant angle of dip are called(a) Isobaric lines(b) Isogonic lines(c) Isoclinic lines(d) Isodynamic lines

In two separate experiments the neutral points due to two small magnets are at a distance of r and 2r in broad side-on position. The ratio of their magnetic moments will be(a) 4 : 1(b) 1 : 2(c) 2 : 1(d) 1 : 8

The line on the earth's surface joining the points where the field is horizontal is(a) Magnetic meridian(b) Magnetic axis(c) Magnetic line(d) Magnetic equator

Intensity of magnetic field due to earth at a point inside a hollow steel box is(a) Less than outside(b) More than outside(c) Same(d) Zero

A magnet of magnetic moment M is rotated through 360° in a magnetic field H, the work done will be(a) MH(b) 2MH(c) 2πMH(d) Zero

The distance of two points on the axis of a magnet from its centre is 10 cm and 20 cm respectively. The ratio of magnetic intensity at these points is 12.5 : 1. The length of the magnet will be(a) 5 cm(b) 25 cm(c) 10 cm(d) 20 cm

Magnetic moments of two bar magnets may be compared with the help of(a)  Deflection magnetometer(b) Vibration magnetometer(c) Both of the above(d) None of the above

A line passing through places having zero value of magnetic dip is called(a) Isoclinic line(b) Agonic line(c) Isogonic line(d) Aclinic line

Ratio between total intensity of magnetic field at equator to poles is(a) 1 : 1(b) 1 : 2(c) 2 : 1(d) 1 : 4

The magnetic field of earth is due to(a) Motion and distribution of some material in and outside the earth(b) Interaction of cosmic rays with the current of earth(c) A magnetic dipole buried at the centre of the earth(d) Induction effect of the sun

A compass needle will show which one of the following directions at the earth's magnetic pole (a) Vertical(b) No particular direction(c) Bent at 45° to the vertical(d) Horizontal

The vertical component of the earth's magnetic field is zero at a place where the angle of dip is(a) 0°(b) 45°(c) 60°(d) 90°

When the N-pole of a bar magnet points towards the south and S-pole towards the north, the null points are at the(a) Magnetic axis(b) Magnetic centre(c) Perpendicular divider of magnetic axis(d) N and S poles

The magnetic field due to the earth is closely equivalent to that due to(a) A large magnet of length equal to the diameter of the earth(b) A magnetic dipole placed at the centre of the earth(c) A large coil carrying current(d) Neither of the above

A bar magnet is placed north-south with its north pole due north. The points of zero magnetic field will be in which direction from the centre of the magnet(a) North and south(b) East and west(c) North-east and south-west(d) North-west and south-east

A dip circle is at right angle to the magnetic meridian. What will be the apparent dip(a) 0°(b) 30°(c) 60°     (d) 90°

At a place, the magnitudes of the horizontal component and total intensity of the magnetic field of the earth are 0.3 and 0.6 Oersted respectively. The value of the angle of dip at this place will be(a) 60°(b) 45°(c) 30°(d) 0°

At the magnetic north pole of the earth, the value of horizontal component of earth's magnetic field and angle of dip are, respectively(a) Zero, maximum(b) Maximum, minimum(c) Maximum, maximum(d) Minimum, minimum

The angle of dip at a place on the earth gives(a) The horizontal component of the earth's magnetic field(b) The location of the geographic meridian(c) The vertical component of the earth's field(d) The direction of the earth's magnetic field

The angle of dip at a place is 60°. At this place the total intensity of earth's magnetic field is 0.64 units. The horizontal intensity of earth's magnetic field at this place is(a) 1.28 units(b) 0.64 units(c) 0.16 units(d) 0.32 units

A dip needle in a plane perpendicular to magnetic meridian will remain (a) Vertical(b) Horizontal(c) In any direction(d)  At an angle of dip to the horizontal

At magnetic poles of earth, angle of dip is

The angle of dip at the magnetic equator is(a) 0°(b) 45°(c) 30°(d) 90°

At a place, if the earth's horizontal and vertical components of magnetic fields are equal, then the angle of dip will be(a) 30°(b)  90°(c) 45° (d)  0°

The lines of forces due to earth's horizontal component of magnetic field are(a) Parallel straight lines(b) Concentric circles(c) Elliptical(d) Parabolic

The vertical component of earth's magnetic field is zero at or The earth's magnetic field always has a vertical component except at the(a) Magnetic poles(b) Geographical poles(c) Every place(d) Magnetic equator

Earth's magnetic field always has a horizontal component except at or Horizontal component of earth's magnetic field remains zero at
 

Rate of change of torque τ with deflection θ is maximum for a magnet suspended freely in a uniform magnetic field of induction B, when(a) θ = 0°(b) θ = 45°(c) θ = 60°(d) θ = 90°

Magnetic lines of force(a) Always intersect(b) Are always closed(c) Tend to crowd far away from the poles of magnet(d) Do not pass through vacuum

If a hole is made at the centre of a bar magnet, then its magnetic moment will(a) Increase(b) Decrease(c) Not change(d) None of these

The period of oscillations of a magnetic needle in a magnetic field is 1.0 sec. If the length of the needle is halved by cutting it, the time period will be(a) 1.0 sec(b) 0.5 sec(c) 0.25 sec(d) 2.0 sec

The strength of the magnetic field in which the magnet of a vibration magnetometer is oscillating is increased 4 times its original value. The frequency of oscillation would then become(a) Twice its original value(b) Four times its original value(c) Half its original value(d) One-fourth its original value

Using a bar magnet P, a vibration magnetometer has time  period 2seconds. When a bar Q (identical to P in mass and size) is placed on top of P, the time period is unchanged. Which of the following statements is true(a) Q is of non-magnetic material(b) Q is a bar magnet identical to P, and its north pole placed on top of P's north pole(c) Q is of unmagnetized ferromagnetic material(d) Nothing can be said about Q's properties

The sensitivity of a tangent galvanometer is increased if(a) Number of turn decreases (b) Number of turn increases(c) Field increases(d) None of the above

A magnetic needle suspended by a silk thread is vibrating in the earth's magnetic field. If the temperature of the needle is increased by 500°C, then(a) The time period decreases(b) The time period remains unchanged(c) The time period increases(d) The needle stops vibrating

Time period in vibration magnetometer will be infinity at(a) Magnetic equator(b) Magnetic poles(c) Equator(d) At all places

Keeping dissimilar poles of two magnets of equal pole strength and length same side, their time period will be(a) Zero(b) One second(c) Infinity(d) Any value

Tangent galvanometer is used to measure(a) Steady currents(b) Current impulses(c) Magnetic moments of bar magnets(d) Earth's magnetic field

Vibration magnetometer works on the principle of(a) Torque acting on the bar magnet(b) Force acting on the bar magnet(c) Both the force and the torque acting on the bar magnet(d) None of these

The time period of oscillation of a magnet in a vibration magnetometer is 1.5 seconds. The time period of oscillation of another magnet similar in size, shape and mass but having one-fourth magnetic moment than that of first magnet, oscillating at same place will be(a) 0.75 sec(b) 1.5 sec(c) 3 sec  (d) 6 sec

To compare magnetic moments of two magnets by vibration magnetometer, 'sum and difference method' is better because(a) Determination of moment of inertia is not needed which minimises the errors(b) Less observations are required(c) Comparatively less calculations(d) All the above

Vibration magnetometer is used for comparing(a) Magnetic fields(b) Earth's field(c) Magnetic moments(d) All of the above

Assertion :   A compass needle when placed on the magnetic north pole of the earth rotates in vertical direction.
Reason     : The earth has only horizontal component of its magnetic field at the north poles.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion :   Gauss theorem is not applicable in magnetism.
Reason    : Mono magnetic pole does not exist.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion  :   For a perfectly diamagnetic substance permeability is always one.
Reason       : The ability of a material of permit the passage of magnetic lines of force through it is called magnetic permeability.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If assertion is false but reason is true.

Assertion   :   The permeability of a ferromagnetic material is independent of the magnetic field.
Reason       : Permeability of a material is a constant quantity.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion :   Reduction factor (K) of a tangent galvanometer helps in reducing deflection to current.
Reason     : Reduction factor increases with increase of current.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion :  Basic difference between an electric line and magnetic line of force is that former is discontinuous and the latter is continuous or endless.
Reason     : No electric lines of forces exist inside a charged body but magnetic lines do exist inside a magnet.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion  :   When a magnetic dipole is placed in a non uniform magnetic field, only a torque acts on the dipole.
Reason      : Force would also acts on dipole if magnetic field were uniform.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion   :   When a magnet is brought near iron nails, only translatory force act on it.
Reason      : The field due to a magnet is generally uniform.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Ratio of magnetic intensities for an axial point and a point on broad side-on position at equal distance d from the centre of magnet will be or The magnetic field at a distance d from a short bar magnet in longitudinal and transverse positions are in the ratio(a) 1 : 1(b) 2 : 3(c) 2 : 1(d) 3 : 2

A curve between magnetic moment and temperature of magnet is

The given figure represents a material which is

The magnetic field lines due to a bar magnet are correctly shown in

Assertion  :   To protect any instrument from external magnetic field, it is put inside an iron body.
Reason      : Iron is a magnetic substance.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion :   A paramagnetic sample display greater magnetisation (for the same magnetising field) when cooled.
Reason     : The magnetisation does not depend on temperature.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion  :   Magnetic moment of an atom is due to both, the orbital motion and spin motion of every electron.
Reason      : A charged particle produces a magnetic field.

Assertion  :   Magnetism is relativistic.
Reason      : When we move along with the charge so that there is no motion relative to us, we find no magnetic field associated with the charge.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion :   The properties of paramagnetic and ferromagnetic substance are not effected by heating.
Reason     : As temperature rises, the alignment of molecular magnets gradually decreases.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If assertion is false but reason is true.

Assertion  :   When radius of circular loop carrying current is doubled, its magnetic moment becomes four times.
Reason      : Magnetic moment depends on area of the loop.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Some equipotential surfaces of the magnetic scalar potential are shown in the figure. Magnetic field at a point in the region is

A short magnet oscillates with a time period 0.1 s at a place where horizontal magnetic field is 24μT. A downward current of 18 A is established in a vertical wire 20 cm east of the magnet. The new time period of oscillator(a) 0.1 s(b) 0.089 s(c) 0.076 s(d) 0.057 s

The unit for molar susceptibility is

Assertion  :  The earth’s magnetic field does not affect the working of a moving coil galvanometer.
Reason     : Earth’s magnetic field is very weak.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Assertion  :   The earth’s magnetic field is due to iron present in its core.
Reason      : At a high temperature magnet losses its magnetic property or magnetism.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If assertion is false but reason is true.

Assertion :  The poles of magnet cannot be separated by breaking into two pieces.
Reason     : The magnetic moment will be reduced to half when a magnet is broken into two equal pieces.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

A diamagnetic material in a magnetic field moves(a) From weaker to the stronger parts of the field(b) Perpendicular to the field(c) From stronger to the weaker parts of the field(d) In none of the above directions

Which curve may best represent the current deflection in a tangent galvanometer

The basic magnetization curve for a ferromagnetic material is shown in figure. Then, the value of relative permeability is highest for the point

Among the following properties describing diamagnetism identify  the property that is wrongly stated(a) Diamagnetic material do not have permanent magnetic moment(b) Diamagnetism is explained in terms of electromagnetic induction(c) Diamagnetic materials have a small positive susceptibility(d) The magnetic moment of individual electrons neutralize each other

In the hysteresis cycle, the value of H needed to make the intensity of magnetisation zero is called(a) Retentivity(b) Coercive force(c) Lorentz force(d) None of the above

Which of the following is diamagnetism(a) Aluminium(b) Quartz(c) Nickel   (d) Bismuth

When a piece of a ferromagnetic substance is put in a uniform magnetic field, the flux density inside it is four times the flux density away from the piece. The magnetic permeability of the material is(a) 1(b) 2(c) 3(d) 4

The magnetic susceptibility of any paramagnetic material changes with absolute temperature T as(a) Directly proportional to T(b) Remains constant(c) Inversely proportional to T(d) Exponentially decaying with T

The materials suitable for making electromagnets should have(a) High retentivity and high coercivity(b) Low retentivity and low coercivity(c) High retentivity and low coercivity(d) Low retentivity and high coercivity

Liquid oxygen remains suspended between two pole faces of a magnet because it is(a) Diamagnetic(b) Paramagnetic(c) Ferromagnetic(d) Antiferromagnetic

Which one of the following is a non-magnetic substance(a) Iron(b) Nickel(c) Cobalt(d) Brass

A frog can be deviated in a magnetic field produced by a current in a vertical solenoid placed below the frog. This is possible because the body of the frog behaves as(a) Paramagnetic(b) Diamagnetic(c) Ferromagnetic(d) Antiferromagnetic

A small rod of bismuth is suspended freely between the poles of a strong electromagnet. It is found to arrange itself at right angles to the magnetic field. This observation establishes that bismuth is(a) Diamagnetic(b) Paramagnetic(c) Ferri-magnetic(d) Antiferro-magnetic

Curie-Weiss law is obeyed by iron at a temperature ......(a) Below Curie temperature(b) Above Curie temperature(c) At Curie temperature only(d) At all temperatures

Which of the following statements is incorrect about hysteresis(a) This effect is common to all ferromagnetic substances(b) The hysteresis loop area is proportional to the thermal energy developed per unit volume of the material(c) The hysteresis loop area is independent of the thermal energy developed per unit volume of the material(d) The shape of the hysteresis loop is characteristic of the material

The universal property of all substances is(a) Diamagnetism(b) Ferromagnetism(c) Paramagnetism(d) All of these

The magnetic susceptibility is negative for(a) Paramagnetic materials(b) Diamagnetic materials(c) Ferromagnetic materials(d) Paramagnetic and ferromagnetic materials

If a magnetic substance is kept in a magnetic field, then which of the following is thrown out(a) Paramagnetic(b) Ferromagnetic(c) Diamagnetic(d) Antiferromagnetic

Susceptibility of ferromagnetic substance is(a) > 1(b) < 1(c) 0  (d) 1

Identify the paramagnetic substance(a) Iron(b) Aluminium(c) Nickel  (d) Hydrogen

The magnetic susceptibility does not depend upon the temperature in(a) Ferrite substances(b) Ferromagnetic substances(c) Diamagnetic substances(d) Paramagnetic substances

Which of the following is true(a) Diamagnetism is temperature dependent(b) Paramagnetism is temperature  dependent(c) Paramagnetism is temperature independent(d) None of these

If a diamagnetic solution is poured into a U-tube and one arm of this U-tube placed between the poles of a strong magnet with the meniscus in a line with the field, then the level of the solution will(a) Rise(b) Fall(c) Oscillate slowly(d) Remain as such

Magnetic permeability is maximum for(a) Diamagnetic substance(b) Paramagnetic substance(c) Ferromagnetic substance(d) All of these

The use of study of hysteresis curve for a given material is to estimate the(a) Voltage loss(b) Hysteresis loss(c) Current loss(d) All of these

An example of a diamagnetic substance is(a) Aluminium(b) Copper(c) Iron   (d) Nickel

Assertion   :   The ferromagnetic substance do not obey Curie’s law.
Reason       : At Curie point a ferromagnetic substance start behaving as a paramagnetic substance.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

Diamagnetic substances are(a) Feebly attracted by magnets(b) Strongly attracted by magnets(c) Feebly repelled by magnets(d) Strongly repelled by magnets

Substances in which the magnetic moment of a single atom is not zero, is known as(a) Diamagnetism(b) Ferromagnetism(c) Paramagnetism(d) Ferrimagnetism

The only property possessed by ferromagnetic substance is(a) Hysteresis(b) Susceptibility(c) Directional property(d) Attracting magnetic substances

Before using the tangent galvanometer, its coil is set in 

The error in measuring the current with a tangent galvanometer is minimum when the deflection is about

Which of the following statement is not the true

When a magnetic substance is heated, then it(a) Becomes a strong magnet(b) Losses its magnetism(c) Does not effect the magnetism(d) Either (a) or (c)

A bar magnet is oscillating in the earth's magnetic field with time period T. If its mass is increased four times then its time period will be (a) 4 T (b) 2T(c) T    (d) T/2

The magnetic susceptibility is

The period of oscillations of a magnet is 2 sec. When it is remagnetised so that the pole strength is 4 times its period will be(a) 4 sec               (b) 2 sec(c) 1 sec  (d) 1/2 sec

The magnet of a vibration magnetometer is heated so as to reduce its magnetic moment by 19%. By doing this the periodic time of the magnetometer will(a) Increase by 19%(b) Decrease by 19%(c) Increase by 11%(d) Decrease by 21%

Two short magnets having magnetic moments in the ratio 27 : 8, when placed on opposite sides of a deflection magnetometer, produce no deflection. If the distance of the weaker magnet is 0.12 m from the centre of deflection magnetometer, the distance of the stronger magnet from the centre is(a) 0.06 m(b) 0.08 m(c) 0.12 m(d) 0.18 m

Which of the following statement is true about magnetic moments of atoms of different elements(a) All have a magnetic moment(b) None has a magnetic moment(c) All acquire a magnetic moment under external magnetic field and in same direction as the field(d) None of the above statements are accurate

At the magnetic poles of the earth, a compass needle will be

Let V and H be the vertical and horizontal components of earth's magnetic field at any point on earth. Near the north pole(a) V >> H(b) V << H (c) V = H  (d) V = H = 0

Isogonic lines on magnetic map will have(a) Zero angle of dip(b) Zero angle of declination(c) Same angle of declination(d) Same angle of dip

At which place, earth's magnetism become horizontal(a) Magnetic pole(b) Geographical pole(c) Magnetic meridian(d) Magnetic equator

A bar magnet is situated on a table along east-west direction in the magnetic field of earth. The number of neutral points, where the magnetic field is zero, are(a) 2(b) 0(c) 1(d) 4

The direction of the null points is on the equatorial line of a bar magnet, when the north pole of the magnet is pointing(a) North(b) South(c) East(d) West

Which of the following relation is correct in magnetism

The value of angle of dip is zero at the magnetic equator because on it(a) V and H are equal(b) The value of V and H is zero(c) The value of V is zero(d) The value of H is zero

Magnetic meridian is a(a) Point(b) Horizontal plane(c) Vertical plane(d) Line along N-S

The magnetic compass is not useful for navigation near the magnetic poles because(a) The magnetic field near the poles is zero(b) The magnetic field near the poles is almost vertical(c) At low temperature, the compass needle looses its magnetic properties(d) Neither of the above

The angle of dip is the angle(a) Between the vertical component of earth's magnetic field and magnetic meridian(b) Between the vertical component of earth's magnetic field and geographical meridian(c) Between the earth's magnetic field direction and horizontal direction(d) Between the magnetic meridian and the geographical meridian

Two like magnetic poles of strength 10 and 40 SI units are separated by a distance 30 cm. The intensity of magnetic field is zero on the line joining them(a) At a point 10 cm from the stronger pole(b) At a point 20 cm from the stronger pole(c) At the mid-point(d) At infinity

Magnetic dipole moment is a(a) Scalar quantity(b) Vector quantity(c) Constant quantity(d) None of these

The torque on a bar magnet due to the earth's magnetic field is maximum when the axis of the magnet is

If a magnet is hanged with its magnetic axis then it stops in(a) Magnetic meridian(b) Geometric meridian(c) Angle of dip(d) None of these

The ultimate individual unit of magnetism in any magnet is called(a) North pole(b) South pole(c) Dipole(d) Quadrupole

Two lines of force due to a bar magnet(a) Intersect at the neutral point(b) Intersect near the poles of the magnet(c) Intersect on the equatorial axis of the magnet(d) Do not intersect at all

There is no couple acting when two bar magnets are placed coaxially separated by a distance because(a) There are no forces on the poles(b) The forces are parallel and their lines of action do not coincide(c) The forces are perpendicular to each other(d) The forces act along the same line

A bar magnet is held perpendicular to a uniform magnetic field. If the couple acting on the magnet is to be halved by rotating it, then the angle by which it is to be rotated is

The intensity of magnetic field is H and moment of magnet is M. The maximum potential energy is(a) MH(b) 2 MH(c) 3 MH (d) 4 MH

The direction of line of magnetic field of bar magnet is(a) From south pole to north pole(b) From north pole to south pole(c) Across the bar magnet(d) From south pole to north pole inside the magnet and from north pole to south pole outside the magnet

A current loop placed in a magnetic field behaves like a(a) Magnetic dipole(b) Magnetic substance(c) Magnetic pole(d) All are true

The magnet can be completely demagnetized by(a) Breaking the magnet into small pieces(b) Heating it slightly(c) Droping it into ice cold water(d) A reverse field of appropriate strength

If a piece of metal was thought to be magnet, which one of the following observations would offer conclusive evidence(a) It attracts a known magnet(b) It repels a known magnet(c) Neither (a) nor (b)(d) It attracts a steel screw driver

For protecting a sensitive equipment from the external magnetic field, it should be(a) Placed inside an aluminium cane(b) Placed inside an iron cane(c) Wrapped with insulation around it when passing current through it(d) Surrounded with fine copper sheet

The incorrect statement regarding the lines of force of the magnetic field B is(a) Magnetic intensity is a measure of lines of force passing through unit area held normal to it(b) Magnetic lines of force form a close curve(c) Inside a magnet, its magnetic lines of force move from north pole of a magnet towards its south pole(d) Due to a magnet magnetic lines of force never cut each other

A short bar magnet placed with its axis at 30° with a uniform external magnetic field of 0.16 Tesla experiences a torque of magnitude 0.032 Joule. The magnetic moment of the bar magnet will be(a) 0.23 Joule/Tesla(b) 0.40 Joule/Tesla(c) 0.80Joule/Tesla(d) Zero

A permanent magnet(a) Attracts all substances(b) Attracts only magnetic substances(c) Attracts magnetic substances and repels all non-magnetic substances(d) Attracts non-magnetic substances and repels magnetic substances

The unit of magnetic moment is

Magnetic lines of force due to a bar magnet do not intersect because(a) A point always has a single net magnetic field(b) The lines have similar charges and so repel each other(c) The lines always diverge from a single point(d) The lines need magnetic lenses to be made to intersect

Force between two identical bar magnets whose centres are r metre apart  is 4.8 N, when their axes are in the same line. If separation is increased to 2r, the force between them is reduced to(a) 2.4N(b) 1.2N(c) 0.6N(d) 0.3N

The work done in turning a magnet of magnetic moment 'M' by an angle of 90° from the meridian is 'n' times the corresponding work done to turn it through an angle of 60°, where 'n' is given by(a) 1/2(b) 2(c) 1/4(d) 1

A sensitive magnetic instrument can be shielded very effectively from outside magnetic fields by placing it inside a box of(a) Teak wood(b) Plastic material(c) Soft iron of high permeability(d) A metal of high conductivity

What happens to the force between magnetic poles when their pole strength and the distance between them are both doubled(a) Force increases to two times the previous value(b) No change(c) Force decreases to half the previous value(d) Force increases to four times the previous value

Magnetic induction is a(a) Scalar quantity(b) Vector quantity(c) Both (a) and (b)(d) None of the above

If the magnetic flux is expressed in weber, then magnetic induction can be expressed in

Magnetic field intensity is defined as(a) Magnetic moment per unit volume(b) Magnetic induction force acting on a unit magnetic pole(c) Number of lines of force crossing per unit area(d) Number of lines of force crossing per unit volume

A long magnet is cut in two parts in such a way that the ratio of their lengths is 2 : 1. The ratio of pole strengths of both the section is(a) Equal(b) In the ratio of 2 : 1(c) In the ratio of 1 : 2(d) In the ratio of 4 : 1

If a bar magnet of magnetic moment M is freely suspended in a uniform magnetic field of strength B, the work done in rotating the magnet through an angle θ is(a) MB(1- sinθ(b) MB sinθ(c) MB cosθ(d) MB(1 – cosθ)

Points A and B are situated perpendicular to the axis of a 2cm long bar magnet at large distances X and 3X from its centre on opposite sides. The ratio of the magnetic fields at A and B will be approximately equal to(a) 1 : 9(b) 2 : 9(c) 27 : 1(d) 9 : 1

In the case of bar magnet, lines of magnetic induction(a) Start from the north pole and end at the south pole(b) Run continuously through the bar and outside(c) Emerge in circular paths from the middle of the bar(d) Are produced only at the north pole like rays of light from a bulb

Which of the following, the most suitable material for making permanent magnet is(a) Steel (b) Soft iron(c) Copper(d) Nickel

The magnetic field due to a short magnet at a point on its axis at distance X cm from the middle point of the magnet is 200 Gauss. The magnetic field at a point on the neutral axis at a distance X cm from the middle of the magnet is(a) 100 Gauss(b) 400 Gauss(c) 50 Gauss(d) 200 Gauss

A magnet is placed in iron powder and then taken out, then maximum iron powder is at(a) Some away from north pole(b) Some away from south pole(c) The middle of the magnet(d) The end of the magnet

A magnet of magnetic moment M and pole strength m is divided in two equal parts, then magnetic moment of each part will be(a) M(b) M/2(c) M/4(d) 2M

Points A and B are situated along the extended axis of 2 cm long bar magnet at a distance x and 2x cm respectively. From the pole nearer to the points, the ratio of the magnetic field at A and B will be (a) 4 : 1 exactly(b) 4 : 1 approx.(c) 8 : 1 exactly(d) 8 : 1 approx.

If a magnet of pole strength m is divided into four parts such that the length and width of each part is half that of initial one, then the pole strength of each part will be(a) m/4(b) m/2(c) m/8(d) 4m

The magnetism of magnet is due to(a) The spin motion of electron(b) Earth(c) Pressure of big magnet inside the earth(d) Cosmic rays

Assertion :   The tangent galvanometer can be made more sensitive by increasing the number of turns of its coil.
Reason    : Current through galvanometer is proportional to the number of turns of coil.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.