CAIE A-Level Physics 10.1 Practical Circuits

Practise reading circuit symbols and diagrams, distinguishing e.m.f. from terminal p.d. and analysing internal resistance, lost volts and load changes.

Exam points

identify and draw practical circuit symbols and interpret complete circuit diagrams
define e.m.f. and distinguish it from p.d. through energy transfer per unit charge
analyse internal resistance, lost volts and terminal p.d. as load current or resistance changes

Covered syllabus points

10.1.1—The circuit symbols shown in section 6 of this syllabus 10.1.2—Draw and interpret circuit diagrams containing the circuit symbols shown in 10.1.3—The electromotive force (e.m.f.) of a source as energy transferred per unit 10.1.4—E.m.f. and potential difference (p.d.) in terms of energy considerations 10.1.5—The effects of the internal resistance of a source of e.m.f. on the terminal

[Maximum number: 1]

Which circuit symbol represents a microphone?

Figure for Question 10.1 Practical circuits question 1 — CAIE A-Level Physics AS — Option A

Figure for Question 10.1 Practical circuits question 1 — CAIE A-Level Physics AS — Option B

Figure for Question 10.1 Practical circuits question 1 — CAIE A-Level Physics AS — Option C

Figure for Question 10.1 Practical circuits question 1 — CAIE A-Level Physics AS — Option D

[Maximum number: 2]

A student uses a circuit containing an ammeter, a voltmeter and a cell to take measurements to determine the resistance of a length of nichrome wire.

Draw a circuit diagram to show how the components should be connected. Use the symbol for a resistor to represent the nichrome wire.

[Maximum number: 5]

(a)

A battery of electromotive force (e.m.f.) 6.0 V and internal resistance r is connected to a resistor of resistance $12 \Omega$ and a variable resistor X, as shown in Fig. 6.2.

Fig. 6.2

[ 5 ]

(i)

By considering energy, explain why the potential difference across the battery's terminals is less than the e.m.f. of the battery.

[ 2 ]

(ii)

A charge of 2.5 kC passes through the battery.

Calculate
1. the total energy transformed by the battery,
energy = J
2. the number of electrons that pass through the battery.
number =

[ 3 ]

1

Energy = EQ

C1

$\begin{aligned} =6.0 \times 2.5 \times 10^{3} =1.5 \times 10^{4} \mathrm{~J} \end{aligned}$

A1

6(b)(ii)2

$\begin{aligned} \text { number } =2.5 \times 10^{3} / 1.6 \times 10^{-19} =1.6 \times 10^{22}\left(1.56 \times 10^{22}\right) \end{aligned}$

A1

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Covered syllabus points

10.1 Practical circuits question 1

10.1 Practical circuits question 2

10.1 Practical circuits question 3

Question (a)

Question (i)

Question (ii)