# CIE AS & A Level Physics : 10.1 Practical circuits – Exam style question – Paper 2

### Question

A uniform electric field is produced between two parallel metal plates. The electric field strength is 1.4 × 104NC–1. The potential difference between the plates is 350V.
(a) Calculate the separation of the plates.
separation = …………………………………………….. m

(b) A nucleus of mass $$8.3 × 10^{–27}$$ kg is now placed in the electric field. The electric force acting on the nucleus is $$6.7 × 10^{–15}$$N.

(i) Calculate the charge on the nucleus in terms of e, where e is the elementary charge.
charge = ……………………………………………… e

(ii) Calculate the mass, in u, of the nucleus.
mass = ……………………………………………… u

(iii) Use your answers in (b)(i) and (b)(ii) to determine the number of neutrons in the nucleus.

number = …………………………………………………

(a)

E = V / d

d = 350 / 1.4 × 104

= 0.025 m

(b)(i)

E = F / Q

Q = 6.7 × 10–15 / 1.4 × 104 (= 4.8 × 10–19 C)

= (4.8 × 10–19 / 1.6 × 10–19) e

= 3.0 e

(b)(ii)

mass = 8.3 × 10–27 / 1.66 × 10–27
= 5.0 u

(b)(iii)

number = 5 – 3
= 2

### Question

(a)Define electric field strength.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………

(b) Two parallel metal plates in a vacuum are separated by a distance of 15mm, as shown in Fig. 6.1. A uniform electric field is produced between the plates by applying a potential difference between them.
A particle of mass 1.7 × 10–27 kg and charge +1.6 × 10–19C is initially at rest at point A on one plate. The particle is moved by the electric field to point B on the other plate. The particle reaches point B with kinetic energy 2.4 × 10–16 J.

(i)Calculate the speed of the particle at point B.

speed = …………………………………………. ms–1

(ii) State the work done by the electric field to move the particle from A to B.
work done = ………………………………………………. J

(iii) Use your answer in (ii) to determine the force on the particle.
force = ……………………………………………… N

(iv) Determine the potential difference between the plates.
potential difference = ……………………………………………… V

(v) On Fig. 6.2, sketch a graph to show the variation of the kinetic energy of the particle with the distance x from point A along the line AB.
Numerical values for the kinetic energy are not required. (a)

force per unit positive charge

(b)(i)

$$E_K = \frac{1}{2}mv^ 2$$

2.4 × 10–16 = ½ × 1.7 × 10–27 × v 2
v = 5.3 × 105 ms–1

(b)(ii)

work done = 2.4 × 10–16 J

(b)(iii)

W = Fs

F = 2.4 × 10–16 /15 × 10–3
= 1.6 × 10–14 N

(b)(iv)

V = Fd /Q
or
V =W/Q
or
E =V/d and E = F/Q

V = (1.6 × 10–14 × 15 × 10–3 )/1.6 × 10–19 or 2.4 × 10–16 /1.6 × 10–19

= 1500 V

(b)(v)

straight line with positive gradient starting at the origin and going as far as x = 15mm

Scroll to Top