A parallel plate capacitor with air between the plates has a capacitance of 8 pF ( 1 pF = 10 - 12 F ) . What will be the capacitance of the distance between the plates is reduced by half, and the space between them is filled with a substance of dielectric constant 6 ?

C = ε ο A d C = 8 p F = 8 × 10 - 12 F ε ο A d = 8 × 10 - 12 L e t t h e n e w c a p a c i tan c e b e C ' C ' = ε o k A d ' , n o w , k = 6 , d ' = d / 2 ∴ C ' = ε o × 6 × A d / 2 = 12 × ε o A d = 12 × 8 × 10 - 12 = 96 × 10 - 12 F = 96 p F .

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Draw the equipotential surface for (a) a dipole and (b) two identical negative charges placed at a certain distance apart.

Important Questions on Electrostatic Potential and Capacitance

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Gamma Question Bank for Medical Physics>Chapter 17 - Electrostatic Potential and Capacitance>Assignment>Q 11

A hollow charged metal sphere has radius

r

. If the potential difference between its surface and a point at a distance

3 r

from the centre is

V

, then electric field intensity at a distance

3 r

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Gamma Question Bank for Medical Physics>Chapter 17 - Electrostatic Potential and Capacitance>Assignment>Q 24

Three charges

- q, Q

and

- q

are placed respectively at equal distances on a straight line. If the potential energy of the system of three charges is zero, then what is the ratio of

Q : q

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Gamma Question Bank for Medical Physics>Chapter 17 - Electrostatic Potential and Capacitance>Assignment>Q 38

Capacitors $C_{1} (10 μF)$ and $C_{2} (20 μ F)$ are connected in series across a $3 kV$ supply, as shown. What is the charge on the capacitor $C_{1}$ ?

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Gamma Question Bank for Medical Physics>Chapter 17 - Electrostatic Potential and Capacitance>Assignment>Q 40

In the circuit below $C_{1} = 20 μF, C_{2} = 40 μF$ and $C_{3} = 50 μF .$ If no capacitor can sustain more than $50 V,$ then maximum potential difference between $X$ and $Y$ is

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Gamma Question Bank for Medical Physics>Chapter 17 - Electrostatic Potential and Capacitance>Assignment>Q 2

Three charges

- Q, - q

and

2 q

are placed at the vertex of equilateral triangle of side length

L .

If potential at centre is zero then correct relation is

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Gamma Question Bank for Medical Physics>Chapter 17 - Electrostatic Potential and Capacitance>Assignment>Q 14

There exists a uniform electric field

E = 4 \times 10^{5} V m^{- 1}

directed along negative

x

-axis such that electric potential at origin is zero. A charge of

- 200 μ C

is placed at origin, and a charge of

+ 200 μ C

is placed at

(3 m, 0) .

The electrostatic potential energy of the system is

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Gamma Question Bank for Medical Physics>Chapter 17 - Electrostatic Potential and Capacitance>Assignment>Q 20

Two metal spheres

A

and

B

of radii

a & b (a < b)

respectively are at a large distance apart. Each sphere carries a charge of

100 μ C .

The spheres are connected by a conducting wire, then

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Gamma Question Bank for Medical Physics>Chapter 17 - Electrostatic Potential and Capacitance>Assignment>Q 41

A hollow metal sphere of radius

10 cm

is charged such that the potential on its surface becomes

80 V

. The potential at the centre of the sphere is

Draw the equipotential surface for (a) a dipole and (b) two identical negative charges placed at a certain distance apart.

Important Questions on Electrostatic Potential and Capacitance

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