# Electrostatics Mock Test-7

Questions No:1

A capacitor of capacity C1, is charged by connecting it across a battery of emf V0. The battery is then removed and the capacitor is connected in parallel with an uncharged capacitor of capacity C2. The potential difference across this combination is

[A] $\frac{C_2}{(C_1+C_2)}$V0

[B] $\frac{C_1}{(C_1+C_2)}$V0

[C] $\frac{C_1+C_2}{(C_2)}$V0

[D] $\frac{ C_1+C_2}{(C_1)}$V0

Questions No:2

A 2µ F condenser is charged up to 200 V and then battery is removed. On combining this with another uncharged condenser in parallel, the potential differences between two plates are found to be 40 V. The capacity of second condenser is

[A] 2µ F

[B] 4µ F

[C] 8µ F

[D] 16µ F

Questions No:3

A capacitor is charged by using a battery which is then disconnected. A dielectric slab is then slipped between the plates which results in

[A] reduction of charges on the plates and increase of potential difference across the plates

[B] increase in the potential difference across the plates, reduction in stored energy, but no change in the charge on the plates

[C] decrease in the potential difference across the plates, reduction in stored energy, but no change in the charge on the plates

[D] None of the above

Questions No:4

Consider two conductors. One of them has a capacity of 2 units and the capacity of the other is unknown. They are charged until their potentials are 4 and 5 units respectively. The two conductors are now connected by a wire when their common potential is found to be 6 units. Then the unknown capacity has the value (in the same units as above)

[A] 6

[B] 5

[C] 4

[D] 3

Questions No:5

If there are n capacitors in parallel connected to V volt source, then the energy stored is equal to

[A] nCV2

[B] $\frac{1}{2}$nV2

[C] $frac{CV2}{n}$

[D] $frac{CV2}{2n}$

Questions No:6

The energy stored in a condenser is in the form of

[A] kinetic energy

[B] potential energy

[C] elastic energy

[D] magnetic energy

Questions No:7

On increasing the plate separation of charged condenser, the energy

[A] increases

[B] decreases

[C] remains unchanged

[D] becomes zero

Questions No:8

The electric potential difference between two parallel plates is 2000 V. If the plates are separated by 2 mm, what is the magnitude of electrostatic force on a charge of 4 x10-6 C located midway between the plates?

[A] 4N

[B] 6N

[C] 8N

[D] 1.5×10-6 N

Questions No:9

A sphere of capacity 2 F can be given a potential of 2 V by

[A] connecting it across a 4 V battery

[B] connecting it to the positive terminal of a 4 V battery and earthing the other terminal

[C] giving it 1 C of charge

[D] giving it 4 C of charge

Questions No:10

The dimensional formula for capacitance is

[A] M-1 L-1 TA

[B] ML T-2A2

[C] M-1 L-2 T4 A2

[D] M-1 L-2 T2 A2

Questions No:11

Two identical capacitors are joined in parallel, charged to a potential V, separated and then connected in series i.e. the positive plate of one is connected to the negative plate of the other. Then

[A] the charges on the free plates connected together are destroyed

[B] charges on the free plates are enhanced

[C] the energy stored in the system increases

[D] the potential difference between the free plates is 2 V

Questions No:12

Two capacitors each having capacitance C and breakdown voltage V are joined in series. The capacitance and the breakdown voltage of the combination will be

[A] 2 C and 2 V

[B] C/2 and V/2

[C] 2Cand V/2

[D] C/2 and 2V

Questions No:13

If the capacitors in the previous question are joined in parallel, the capacitance and the breakdown voltage of the combination will be

[A] 2Cand2V

[B] C and 2V

[C] 2 C and V

[D] C and V

Questions No:14

Two spherical conductors each of capacity C are charged to potential V and -V. These are then connected by means of a fine wire. The loss of energy is

[A] zero

[B] $frac{1}{2}$$CV^2$

[C] $CV^2$

[D] $2CV^2$

Questions No:15

A soap bubble is given a negative charge, then its radius

[A] decreases

[B] increases

[C] remains unchanged

[D] nothing can be predicted as information is insufficient

Questions No:16

Dielectric constant of pure water is 8 Its permittivity will be

[A] 7.17 x 10-10 MKS units

[B] 8.86 x 10-12 MKS units

[C] 1.02 X1013 MKS units

[D] Cannot be calculated

Questions No:17

There are two metallic spheres of same radii but one is solid and the other is hollow, then

[A] solid sphere can be given more charge

[B] hollow sphere can be given more charge

[C] they can be charged equally (maximum)

[D] None of the above

Questions No:18

Dielectric constant for metal is

[A] zero

[B] infinite

[C] 1

[D] None of these

Questions No:19

Two spheres A and B of radius 4 cm and 6 cm are given charges of 80 µ C and 40 µ C respectively. If they are connected by a fine wire, the amount of charge flowing from one to the other is

[A] 20 µ C from A to B

[B] 20 µ C from B to A

[C] 32 µ C from Bio A

[D] 32 µ C from A to B

Questions No:20

In Millikan’s oil drop experiment an oil drop carrying a charge Q is held stationary by a potential difference 2400 V between the plates. To keep a drop of half the radius stationary the potential difference had to be made 600 V. What is the charge on the second drop

[A] $\frac{Q}{4}$

[B] $\frac{Q}{2}$

[C] Q

[D] $\frac{3Q}{2}$