Page 31 - Electrostatics 11

Grade 11 © GC Shiba

4 Two large parallel metal plates carry opposite charges. They are separated
by 0.20 m and the p.d. between them is 500 V. What is the magnitude of

electric field, if it is uniform, in the region between them?

Ans: 2500 V/m
5 What distance must an electron move in a uniform potential gradient

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200 V cm in order to gain kinetic energy 3.2 × 10 ?
Ans: 0.001 m
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6 An electron of mass 9.1 × 10 kg and charge 1.6 × 10 C is situated in a
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uniform electric field of intensity 1.2 × 10 Vm . Find the time it takes to
travel 1 cm from rest.
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Ans: 3.1 × 10 Sec
7 A solid sphere of radius 1 cm is carrying a charge of 2 C. Find the electric
field intensity at the centre, on its surface and at a point 2 cm from the

centre of the charged sphere.

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Ans: 1.8 × 10 N/C, 4.5 × 10 N/C
8 An alpha particle is a nucleus of doubly ionized helium. It has mass of 6.68
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× 10 kg and charge of 3.2 × 10 C. Compare the force of electrostatic
repulsion between the two alpha particles with the force of gravitational
attraction between them.

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Ans: 3.1 × 10 N
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9 An electron of charge 1.6 × 10 C is situated in a uniform electric field
intensity 120,000 V/m. Find the force on it and its acceleration.
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Ans: 1.92 × 10 N, 2.1 × 10 m/s 2

10 Calculate the value of two equal charges if they repel one another with a

force on 0.1 N when situated 50 cm apart in vacuum. What would be the
distance between them if they are placed in an insulating medium of

dielectric constant 10 ?
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Ans: 1.67 × 10 C, 0.16 m
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11 Two charges +1 × 10 and -4 × 10 C are separated by a distance of 2 m.
Determine the position of null point.
Ans: 2 m from small charge

12 Two horizontal parallel plates, 20 mm apart, have a potential difference of

1000 V between them the upper plate being at a positive potential. A
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negatively charged oil drop, mass 4.8 × 10 Kg, is situated between the
31 Electrostatics