﻿ Two small balls, each carrying a charge q are suspended by e

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## Electrostatic Potential and Capacitance

#### Multiple Choice Questions

161.

Three capacitors of capacitances 1 µF, 2µF and 4μF are connected first in a series combination and then in a parallel combination. The ratio their equivalent capacitances will be

• 2 : 49

• 49 : 2

• 4 : 49

• 49 : 4

162.

A parallel plate capacitor with air as the dielectric has capacitance C. A slab of dielectric constant K and having the same thickness as the separation between the plates is introduced so as to fill one-fourth of the capacitor as shown in the figure. The new capacitance will be

• $\frac{\mathrm{KC}}{4}$

163.

A parallel palte condenser is filled with two dielectrics as shown in figure. Area of each pate is A m2 and the separation is d metre. The dielectric constants are K1 and K2 respectively. Its capacitance in farad will be

164.

Two equal negative charges - q are fixed at the point (0, a) and (0, - a) on the y-axis. A positive charge Q is released from rest at the point (2a, 0) on the x-axis. The charge wil

• execute SHM about the origin

• move to the origin and remain at rest

• move to infinity

• execute oscillatory but not SHM

165.

A charged particle is accelerated by a potential of 200 V. If its velocity is 8.4 × 108 m/s, then value  of e/m for that particle is

• 17.6 × 1016

• 14.5 × 1012

• 1.76 × 1015

• 1.45 × 1015

166.

Two capacitors of capacities C1 and C2 are charged upto the potential V1 and V2 then condition for not flowing the charge between on connected them in parallel is

• C1 = C2

• C1V1 = C2V2

• V1 =V2

167.

If V =ary, then electric field at a point will be proportional to

• r

• -1

• r -2

• r2

168.

Electric field at point 20 cm away from the centre of dielectric sphere is 100 V/m, radius of sphere is 10 cm, then the value of electric field at a distance 3 cm from the centre is

• 100 V/m

• 125 V/m

• 120 V/m

• 0

169.

Magnetic field of the earth is H =0.3 g. A magnet is vibrating 5 oscillations per min then the dippreciation required in the magnetic field of the earth of increase time period upto 10 oscillations per minute is

• 2.25 g

• 0.6 g

• 0.9 g

• 0.12 g

# 170.Two small balls, each carrying a charge q are suspended by equal insulator strings of length l m from the hook of a stand. This arrangement is carried in a satellite in space. The tension in each string will be

B.

Suppose, T be the tension in the spring T. Also in the satellite, two balls will be in a straight line.

So, force acting on the balls
F =               ......(i)

This force will be balanced by tension in the string

T = F                          ......(ii)

Now from equatin (i) and (ii) we get

T =