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Electric Fields - Multiple Choice Questions

Q1. Two parallel metal plates of separation a carry equal and opposite charges.

Which graph best represents how the electric field strength E varies with the distance x in the space between the two plates?

 

This is a uniform field as the field lines are parallel - therefore the electric field strength between the plates is constant.

E = V/a and does not depend on 'x'

Q2. A particle has a mass m and a charge q. It is accelerated through a potential difference V, over a distance d.

What is the average acceleration of the particle?

F = ma

so a = F/m

For a charged particle F = EQ

but E = V/d so F = VQ/d

so, a = VQ/(dm)

Choice A

Q3. An electron moves through a distance of 0.10 m parallel to the field lines of a uniform electric field of strength 2.0 kN C−1 .

What is the work done on the electron?

A
zero
B
1.6 × 10−17 J
C
3.2 × 10−17 J
D
1.6 × 10−21 J

 

Work done = Force x distance moved in the direction of the force.

W = Fd

W = EQd

W = 2.0 x 103 x 1.6 x 10-19 x 0.10

W = 3.2 x 10-17 J

Choice C