Physics M.C.Q (1 Marks)

A metallic shell has a point charge ‘q’ kept inside its cavity. Which one of the following diagrams correctly represents the electric lines of forces

and  are point charges located at points as shown in the figure and S is a spherical Gaussian surface of radius R. Which of the following is true according to the Gauss’s law

A charge q is placed at the centre of the line joining two  equal charges  Q. The system of the three charges will be in equilibrium, if q is equal to

(a)

(b)

(b)

(d)

A capacitor when filled with a dielectric K = 3  has charge , voltage  and field . If the dielectric is replaced with another one having K = 9  the new values of charge, voltage and field will be respectively

(a)

(b)

(c)

(d)

Inside a hollow charged spherical conductor, the potential

An uncharged sphere of metal is placed in between two charged plates as shown. The lines of force look like

In the circuit shown in the figure, the potential difference across the 4.5mF capacitor is

What is the effective capacitance between A and B in the following figure

Between the plates of a parallel plate capacitor a dielectric plate is introduced just to fill the space between the plates. The capacitor is charged and later disconnected from the battery. The dielectric plate is slowly drawn out of the capacitor parallel to the plates. The plot of the potential difference across the plates and the length of the dielectric plate drawn out is

Which one statement is correct ? A parallel plate air condenser is connected with a battery. Its charge, potential, electric field and energy are  and respectively. In order to fill the complete space between the plates a dielectric slab is inserted, the battery is still connected. Now the corresponding values Q, V, E  and U are in relation with the initially stated as 

Consider the charge configuration and spherical Gaussian surface as shown in the figure. When calculating the flux of the electric field over the spherical surface the electric field will be due to

An electron moving with the speed 5   per sec is shooted parallel to the electric field of intensity 1 . Field is responsible for the retardation of motion of electron. Now evaluate the distance travelled by the electron before coming to rest for an instant (mass of e = 9 .  charge = 1.6 )

The distance between charges 5 ×   and -2.7   is 0.2 m. The distance at which a third charge should be placed in order that it will not experience any force along the line joining the two charges is

In the figure the charge Q is at the centre of the circle. Work done is maximum when another charge is taken from point P to

ABC is an equilateral triangle. Charges + q are placed at each corner. The electric intensity at O will be

Three charges each of magnitude q are placed at the corners of an equilateral triangle, the electrostatic force on the charge placed at the center is (each side of triangle is L)

The variation of potential with distance R from a fixed point is as shown below. The electric field at R = 5 m is

A positively charged thin metal ring of radius R  is fixed in the xy - plane with its centre at the O. A negatively charged particle P  is released from rest at the point  (0, 0,  where  . Then the motion of  P is

A charged particle q is shot towards another charged particle Q which is fixed, with a speed v. It approaches Q upto a closest distance r and then returns. If q were given a speed 2v, the closest distances of approach would be

Four condensers are joined as shown in the adjoining figure. The capacity of each is 8 μF. The equivalent capacity between the points A and  B will be

A parallel plate capacitor of capacity  is charged to a potential

(i)   The energy stored in the capacitor when the battery is disconnected and the separation is doubled  

(ii) The energy stored in the capacitor when the charging battery is kept connected and the separation between the capacitor plates is doubled is Then   value is

A cube of side b  has a charge q at each of its vertices. The electric field due to this charge distribution at the centre of this cube will be

A metallic solid sphere is placed in a uniform electric field. The lines of force follow the path(s) shown in figure as

Four charges are arranged at the corners of a square ABCD, as shown in the adjoining figure. The force on the charge kept at the centre O is

The electric field due to a uniformly charged sphere of radius R as a function of the distance from its centre is represented graphically by

Assertion  :   A parallel plate capacitor is connected across battery through a key. A dielectric slab of constant K is introduced between the plates. The energy which is stored becomes K times.

Reason     : The surface density of charge on the plate remains constant or unchanged.

Assertion  :   The tyres of aircraft's are slightly conducting.

Reason      : If a conductor is connected to ground, the extra charge induced on conductor will flow to ground.

Assertion  :   Circuit containing capacitors should be handled cautiously even when there is no current.

Reason      : The capacitors are very delicate and so quickly break down.

Assertion  :   At a point in space, the electric field points towards north. In the region, surrounding this point the rate of change of potential will be zero along the east and west.

Reason     : Electric field due to a charge is the space around the charge.

Assertion  :   Conductors having equal positive charge and volume, must also have same potential.

Reason     :   Potential depends only on charge and volume of conductor.

Assertion  :   The whole charge of a conductor cannot be transferred to another isolated conductor.

Reason     : The total transfer of charge from one to another is not possible.

Assertion  :   On going away from a point charge or a small electric dipole, electric field decreases at the same rate in both the cases.

Reason      : Electric field is inversely proportional to square of distance from the charge or an electric dipole.

Assertion  :   The surface charge densities of two spherical conductors of different radii are equal. Then the electric field intensities near their surface are also equal.

Reason    : Surface charge density is equal to charge per unit area.

Assertion :   If a point charge q is placed in front of an infinite grounded conducting plane surface, the point charge will experience a force.

Reason     : This force is due to the induced charge on the conducting surface which is at zero potential.

Assertion :   Charge is quantized

Reason    : Charge, which is less than 1 C is not possible

Assertion :   The capacity of a given conductor remains same even if charge is varied on it.

Reason      : Capacitance depends upon nearly medium as well as size and shape of conductor.

Assertion  :   When charges are shared between any two bodies, no charge is really lost, but some loss of energy does occur.

Reason      : Some energy disappears in the form of heat, sparking etc.

Assertion  :   Dielectric breakdown occurs under the influence of an intense light beam.

Reason      : Electromagnetic radiations exert pressure.

Assertion  :   If a proton and an electron are placed in the same uniform electric field. They experience different acceleration.

Reason     : Electric force on a test charge is independent of its mass.

Assertion  :   Electric lines of force cross each other.

Reason      : Electric field at a point superimpose to give one resultant electric field.

Four metallic plates each with a surface area of one side A are placed at a distance d from each other. The plates are connected as shown in the circuit diagram. Then the capacitance of the system between a  and b  is

Assertion  :   If three capacitors of capacitance C₁ < C₂ < C₃ are connected in parallel then their equivalent capacitance C_p > C_s

Reason      : 

Assertion   :   A metallic shield in form of a hollow shell may be built to block an electric field.

Reason       : In a hollow spherical shield, the electric field inside it is zero at every point.

Figure (a) shows two capacitors connected in series and joined to a battery. The graph in figure (b) shows the variation in potential as one moves from left to right on the branch containing the capacitors, if

A fully charged capacitor has a capacitance ‘C’. It is discharged through a small coil of resistance wire embedded in a thermally insulated block of specific heat capacity ‘s’ and mass ‘m’. If the temperature of the block is raised by ‘ ∆T ’, the potential difference ‘V’ across the capacitance is

The plates of a parallel plate condenser are pulled apart with a velocity v. If at any instant their mutual distance of separation is d, then the magnitude of the time of rate of change of capacity depends on d as follows

The plates of a capacitor are charged to a potential difference of 320 volts and are then connected across a resistor. The potential difference across the capacitor decays exponentially with time. After 1 second  the potential difference between the plates of the capacitor is 240 volts, then after 2 and 3 seconds the potential difference between the plates will be

Assertion   :   Charge is invariant.

Reason      : Charge does not depends on speed of frame of reference.

Figure given below shows two identical parallel plate capacitors connected to a battery with switch S closed. The switch is now opened and the free space between the plate of capacitors is filled with a dielectric of dielectric constant 3. What will be the ratio of total electrostatic energy stored in both capacitors before and after the introduction of the dielectric

In an RC circuit while charging, the graph of in i versus time is as shown by the dotted line in the diagram figure, where i is the current. When the value of the resistance is doubled, which of the solid curve best represents the variation of in i versus time