IIT NEET Physics Electrostatics

Electrostatics Mock Test-6

Questions No:1

A parallel plate condenser with air between the plates possesses the capacity of 10-12 F. Now the plates are removed apart, so that the separation is twice the original value. The space between the plates is filled with a material of dielectric constant Then new value of the capacity is (in farad)

[A] 4X1012

[B] 3×1012

[C] 2×1012

[D] 0.5×1012

Questions No:2

Three condensers each of capacity C microfarad are connected in series. An exactly similar set is connected in parallel to the first one. The effective capacity of the combination is 4µ F. Then the value of C in microfarad is

[A] 8

[B] 6

[C] 4

[D] 2

Questions No:3

The capacitance of the earth, viewed as a spherical conductor of radius 6408 km is

[A] 980 µ F

[B] 1424µ F

[C] 712µ F

[D] 356µ F

Questions No:4

Eight drops of mercury of equal radii combine to form a big drop. The capacitance of the bigger drop as compared to each smaller drop is

[A] 2 times

[B] 8 times

[C] 4 times

[D] 16 times

Questions No:5

The capacity of a spherical condenser is 1 µ F. If the spacing between the two spheres is 1 mm, the radius of the outer sphere is

[A] 30 cm

[B] 3 cm

[C] 6m

[D] 3 m

Questions No:6

A thin metal plate P is inserted between the plates of a parallel-plate capacitor of capacitance C in such a way that its edges touch the two plates. The capacitance now becomes

[A] \( \frac{c}{2} \)

[B] 2C

[C] zero

[D] (d

Questions No:7

The capacitance of a capacitor does not depend on

[A] the medium between the plates

[B] the size of the plates

[C] the charges on the plates

[D] the separation between the plates

Questions No:8

A parallel plate capacitor has plate separation d and 2 capacitance25 µ F. If a metallic foil of thickness \( \frac{2}{7} \) d is introduced between the plates, the capacitance would become

[A] 25µ F

[B] 35µ F

[C] \( \frac{125}{7} \) µ F

[D] \( \frac{175}{2} \)µ F

Questions No:9

In a charged capacitor, the energy resides in

[A] the positive charges

[B] both the positive and negative charges

[C] the field between the plates

[D] around the edge of the capacitor plates

Questions No:10

A capacitor of capacity C has charge Q and stored energy is W. If the charge is increased to 2Q, the stored energy will be

[A] 2W

[B] \( \frac{W}{2} \)

[C] 4W

[D] \( \frac{W}{4} \)

Questions No:11

The capacity and the energy stored in a charged parallel plate condenser with air between its plates are respectively C0 and W0. If the air is replaced by glass (dielectric constant = 5) between the plates, the capacity of the plates and the energy stored in it will respectively be

[A] 5C0, 5W0

[B] 5C0, \( \frac{W_0}{5}\)

[C] \( \frac{C_0}{5}\),\( 5W_0 \)

[D] \( \frac{C_0}{5}\) , \( \frac{W_0}{5}\)

Questions No:12

A capacitor of capacity C is connected with a battery of potential V. The distance between its plates is reduced to half, assuming that the battery remains the same. Then the new energy given by the battery will be

[A] \( \frac{CV^2}{4} \)

[B] \( \frac{CV^2}{2} \)

[C] \( \frac{3CV^2}{4} \)

[D] \( CV^2 \)

Questions No:13

A charged capacitor when filled with a dielectric K =3 has charge Q0, voltage V0 and field E0. If the dielectric is replaced with another one having K = 9 the new values of charge voltage and field will be respectively

[A] 3Q0, 3V0. 3E0

[B] Q0, 3V0, 3E0

[C] Q0,\( \frac{V_0}{3} \),3E0

[D] Q0,\( \frac{V_0}{3} \),\( \frac{E_0}{3} \)

Questions No:14

A 2 µF capacitor is charged to 100 V and then its plates are connected by a conducting wire. The heat produced is

[A] 1 J

[B] 0.1 J

[C] 0.01 J

[D] 0.001 J

Questions No:15

The force between the plates of a parallel plate capacitor of capacitance C and distance of separation of the plates d with a potential difference V between the plates, is

[A] \( \frac{CV^2}{2d} \)

[B] \( \frac{C^2V^2}{2d} \)

[C] \( \frac{C^2V^2}{d^2} \)

[D] \( \frac{V^2d}{C} \)

Questions No:16

A parallel plate air capacitor is charged to a potential difference of V. After disconnecting the battery, distance between the plates of the capacitor is increased using an insulating handle. As a result, the potential difference between the plates

[A] decreases

[B] increases

[C] becomes zero

[D] does not change

Questions No:17

A variable condenser is permanently connected to a 100 V battery. If the capacity is changed from 2 µF to 10 µF then change in energy is equal to

[A] 2 x10 -2 J

[B] 2.5 x 10-2 J

[C] 3.5X10-2 J

[D] 4X10-2 J

Questions No:18

Two condensers of capacity 3µF and 6µF respectively are connected in series. The combination is connected across a potential of 6 V. The ratio of energies stored by the condensers will be

[A] \( \frac{1}{2} \)

[B] 2

[C] \( \frac{1}{4} \)

[D] 4

Questions No:19

Three capacitors of 2µF, 3µF and 6µlF are joined in series and the combination is charged by means of a 24 V battery. The potential difference between the plates of the 6 µF capacitor is

[A] 4V

[B] 6 V

[C] 8V

[D] 10 V

Questions No:20

A dielectric slab of thickness d is inserted in a parallel plate capacitor whose negative plate is at x = 0 and positive plate is at x = 3d. The slab is equidistant from the plates. The capacitor is given some charge. As one goes from 0 to 3d

[A] the magnitude of the electric field remains the same

[B] the direction of the electric field remains the same

[C] the electric potential increases continuously

[D] the electric potential increases at first, then decreases and again increases