Physics M.C.Q [1M]

A proton (or charged particle) moving with velocity v is acted upon by electric field E and magnetic field B. The proton will move undeflected if

(a) E is perpendicular to B

(b) E is parallel to v and perpendicular to B

(c) E, B and v are mutually perpendicular and

(d) E and B both are parallel to v

Wires 1 and 2 carrying currents  and  respectively are inclined at an angle  θ to each other. What is the force on a small element dl of wire 2 at a distance of r from wire 1 (as shown in figure) due to the magnetic field of wire1

(a)

(b)

(c)

(d)

A steady current i flows in a small square loop of wire of side L in a horizontal plane. The loop is now folded about its middle such that half of it lies in a vertical plane. Let   and   respectively denote the magnetic moments due to the current loop before and after folding. Then

(a)	(b)  and   are in the same direction
(c)	(d)

What will be the resultant magnetic field at origin due to four infinite length wires. If each wire produces magnetic field 'B' at origin

(a) 4 B

(b)

(c) 2

(d) Zero

A metallic block carrying current I is subjected to a uniform magnetic induction  as shown in the figure. The moving charges experience a force  given by ........... which results in the lowering of the potential of the face ........ Assume the speed of the carriers to be v

(a) eVB, ABCD

(b) eVB, EFGH

(c) -eVB, ABCD

(d) -eVB, EFGH

Two coaxial solenoids 1 and 2 of the same length are set so that one is inside the other. The number of turns per unit length are   and . The currents  and  are flowing in opposite directions. The magnetic field inside the inner coil is zero. This is possible when

(a)  and	(b)
(c)   and	(d)

Two straight long conductors AOB and COD are perpendicular to each other and carry currents  and . The magnitude of the magnetic induction at a point P at a distance a from the point O in a direction perpendicular to the plane ACBD is

(a)  (

(b)

(c)

(d)

A coil having N turns is wound tightly in the form of a spiral with inner and outer radii a and b respectively. When a current I passes through the coil, the magnetic field at the centre is

(a)

(b)

(c)

(d)

Current i is carried in a wire of length L. If the wire is turned into a circular coil, the maximum magnitude of torque in a given magnetic field B will be

(a)

(a)

(c)

(d)

Two long straight parallel conductors separated by a distance of 0.5m carry currents of 5A and 8A in the same direction. The force per unit length experienced by each other is

(a) 1.3  (attractive)	(b) 1.6   (repulsive)
(c) 16  (attractive)	(d) 16  (repulsive)

A circular coil of radius 4 cm and of 20 turns carries a current of 3 amperes. It is placed in a magnetic field of intensity of 0.5 . The magnetic dipole moment of the coil is

(a) 0.15

(b) 0.3

(c) 0.45

(d) 0.6

The relation between voltage sensitivity () and current sensitivity () of a moving coil galvanometer is (Resistance of Galvanometer = G)

(a)

(b)

(c)

(d)

A long wire A carries a current of 10 amp. Another long wire B, Which is parallel to A and separated by 0.1m from A, carries a current of 5 amp, in the opposite direction to that in A. what is the magnitude and nature of the force experienced per unit length of B  (

(a) Repulsive force of	(b) Attractive force of
(c) Repulsive force of 2π ×	(d) Attractive force of 2π

What is the net force on the square coil

(a) 25  moving towards wire	(b) 25  moving away from wire
(c) 35   moving towards wire	(d) 35   moving away from wire

A circular coil of diameter 7cm has 24 turns of wire carrying current of 0.75A. The magnetic moment of the coil is

(a) 6.9	(b) 2.3
(c)	(d)

A power line lies along the east-west direction and carries a current of 10 ampere. The force per metre due to the earth's magnetic field of   is

(a)

(b)

(c)

(d)

AB  and CD are long straight conductor, distance d apart, carrying a current I. The magnetic field at the midpoint of BC is

(a)

(b)

(c)

(d)

Due to the flow of current in a circular loop of radius R, the magnetic induction produced at the centre of the loop is B. The magnetic moment of the loop is (

(a)

(b)

(c)

(d)

Three long, straight and parallel wires carrying currents are arranged as shown in figure. The force experienced by 10 cm length of wire Q is

(a) 1.4  towards the right	(b) 1.4  towards the left
(c) 2.6  to the right	(d) 2.6  to the left

A circular loop has a radius of 5 cm and it is carrying a current of 0.1 amp. Its magnetic moment is

(a) 1.32	(b) 2.62
(c) 5.25	(d) 7.85

Two parallel wires in free space are 10 cm apart and each carries a current of 10 A in the same direction. The force one wire exerts on the other per metre of length is

(a) 2 , attractive	(b) 2, repulsive
(c) 2  , attractive	(d) 2  , repulsive

A, B and C are parallel conductors of equal length carrying currents I, I and 2I respectively. Distance between A and B is x. Distance between B and C is also x.   is the force exerted by B on A and F₂ is the force exerted by B on A choose the correct answer

(a)

(b)

(c)

(d)

The radius of a circular loop is r and a current i  is flowing in it. The equivalent magnetic moment will be

(a) ir

(b) 2πir

(c) iπ

(d)

Two straight parallel wires, both carrying 10 ampere in the same direction attract each other with a force of 1. If both currents are doubled, the force of attraction will be

(a) 1

(b) 2

(c) 4

(d) 0.25

Through two parallel wires A and B, 10 and 2 ampere of currents are passed respectively in opposite direction. If the wire A is infinitely long and the length of the wire B is 2 m, the force on the conductor B, which is situated at 10 cm distance from A will be

(a) 8

(a) 8

(c) 4

(d) 4π

3 A of current is flowing in a linear conductor having a length of 40 cm. The conductor is placed in a magnetic field of strength 500 gauss and makes an angle of 30° with the direction of the field. It experiences a force of magnitude

(a) 3

(b) 3

(c) 3

(d) 3

A triangular loop of side l carries a current I. It is placed in a magnetic field B such that the plane of the loop is in the direction of B. The torque on the loop is

(a) Zero

(b) IBl

(c)

(d)

An electron enters a region where electrostatic field is 20N/C and magnetic field is 5T. If electron passes undeflected through the region, then velocity of electron will be

(a)

(b)

(c)

(d)

A charged particle is moving in a uniform magnetic field in a circular path. Radius of circular path is R. When energy of particle is doubled, then new radius will be

(a) R

(b)

(c) 2 R

(d) 3 R

A proton moving with a velocity, 2.5  , enters a magnetic field of intensity 2.5T making an angle 30°  with the magnetic field. The force on the proton is

(a) 3

(b) 5

(c) 6

(d) 9

A proton and a deutron both having the same kinetic energy, enter perpendicularly into a uniform magnetic field B. For motion of proton and deutron on circular path of radius   and   respectively, the correct statement is

(a)

(b)

(c)

(d)

A proton, a deuteron and an α - particle having the same kinetic energy are moving in circular trajectories in a constant magnetic field. If   and   denote respectively the radii of the trajectories of these particles, then

(a)

(b)

(c)

(d)

A proton of mass 1.67   and charge 1.6   is projected with a speed of 2  m/s at an angle of 60°  to the X - axis. If a uniform magnetic field of 0.104 Tesla is applied along Y - axis, the path of proton is

(a) A circle of radius = 0.2 m and time period

(b) A circle of radius = 0.1 m and time period 2

(c) A helix of radius = 0.1 m and time period 2

(d) A helix of radius = 0.2 m and time period  4

Two long and parallel wires are at a distance of 0.1 m and a current of 5 A is flowing in each of these wires. The force per unit length due to these wires will be

(a) 5

(b) 5

(c) 2.5

(d) 2.5

A particle with   of charge and   mass is moving with a velocity of   along the y-axis. A uniform static magnetic field B = 0.5 Tesla  is acting along the x-direction. The force on the particle is

(a) 5 ×   along	(b) 5   along
(c)  5 ×  along -	(d) 5   along  -

A beam of well collimated cathode rays travelling with a speed of 5   enter a region of mutually perpendicular electric and magnetic fields and emerge undeviated from this region. If |B| = 0.02T, the magnitude of the electric field is

(a)

(b) 2.5

(c) 1.25

(d) 2

n electron is moving on a circular path of radius r with speed v in a transverse magnetic field B. e/m for it will be

(a)

(b)

(c) Bvr

(d)

A 2 MeV proton is moving perpendicular to a uniform magnetic field of 2.5 tesla. The force on the proton is

(a) 2.5

(b) 7.6

(c) 2.5

(d) 7.6

An electron and a proton enter region of uniform magnetic field in a direction at right angles to the field with the same kinetic energy. They describe circular paths of radius   and   respectively. Then

(a)

(b)

(c)

(d)  may be less than or greater than   depending on the direction of the magnetic field

Two infinite length wires carries currents 8A and 6A respectively and placed along X and Y-axis. Magnetic field at a point P(0, 0, d)m will be

(a)

(b)

(c)

(d)

A uniform magnetic field B is acting from south to north and is of magnitude 1.5 . If a proton having mass  = 1.7   and charge  = 1.6   moves in this field vertically downwards with energy 5 MeV, then the force acting on it will be

(a) 7.4

(b) 7.4

(c) 7.4

(d) 7.4

Two concentric coils each of radius equal to 2π cm are placed at right angles to each other. 3 ampere and 4 ampere are the currents flowing in each coil respectively. The magnetic induction in   at the centre of the coils will be (

(a) 5

(b) 7

(c) 12

(d)

A coil having N turns carry a current I as shown in the figure. The magnetic field intensity at point P is

(a)

(b)

(c)

(d) Zero

A part of a long wire carrying a current i is bent into a circle of radius r as shown in figure. The net magnetic field at the centre O of the circular loop is

(a)

(b)

(c)

(d)

When a certain length of wire is turned into one circular loop, the magnetic induction at the centre of coil due to some current flowing is  If the same wire is turned into three loops to make a circular coil, the magnetic induction at the center of this coil for the same current will be

(a)

(b) 9

(c) 3

(d) 27

A long straight wire carries a current of π amp. The magnetic field due to it will be 5  at what distance from the wire [ permeability of air]

(a)   metre

(b)  metre

(c)  metre

(d)  metre

A long solenoid has n turns per meter and current I A is flowing through it. The magnetic field at the ends of the solenoid is

(a)

(b)

(c) Zero

(d) 2

The dimension of the magnetic field intensity B is

(a)

(b)

(c)

(d)

An electric current passes through a long straight wire. At a distance 5 cm from the wire, The magnetic field is B. The field at 20 cm  from the wire would be

(a)

(b)

(c)

(d)

A circular loop of radius 0.0157m carries a current of 2.0 amp. The magnetic field at the centre of the loop is (

(a) 1.57	(b) 8.0
(c) 2.5	(d)  3.14