Syllabus Edition

First teaching 2020

Last exams 2024

10.1 DC: Practical Circuits & Kirchhoff's Laws

Easy

Medium

3 marks

Three resistors of resistances R₁, R₂ and R₃ are connected as shown in Fig. 1.1.

Fig 1.1

The potential difference across the resistors are V₁, V₂ and V₃. The current in the combination of resistors is I.

Show that the total resistance R of the combination is given by the equation.

R = R_{1} + R_{2} + R_{3}

How did you do?

3 marks

Three resistors are placed in a circuit with a cell of 10 V and negligible internal resistance and two switches S₁ and S₂. This is shown in Fig 1.1.

Fig 1.1

Complete table 1.1.

Table 1.1

Position of switches
S₁	S₂	Total resistance / kΩ
open	closed
closed	open
closed	closed

How did you do?

2 marks

The cell has an e .m .f of 10 V and negligible internal resistance.

Calculate the current from the cell when

(i)

switch S₁ is closed,

[1]

(ii)

both S₁ and S₂ are closed.

[1]

How did you do?

3 marks

Using your answers in part (c), determine the current from the cell if just switch S₂ is closed.

How did you do?

Did this page help you?

2 marks

Three resistors of resistances R₁, R₂ and R₃ are connected as shown in Fig. 1.1.

The currents in the resistors are I₁, I₂ and I₃. The total current in the combination of resistors is I and the potential difference across the combination is V.

Show that the total resistance R of the combination is given by the equation

$\frac{1}{R} = \frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{3}}$

How did you do?

10 marks

A battery of electromotive force (e.m.f.) 6.0 V and internal resistance r is connected to an external resistor of resistance 12 Ω and a thermistor X, as shown in Fig. 1.2.

q6b-paper-2-specimen-2022-cie-ial-physics

Fig. 1.2

(i)

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

[1]

(ii)

A charge of 2.5 kC passes through the battery.

Calculate:

• the total energy transferred by the battery

energy = ............................................................ J

• the number of electrons that pass through the battery.

number = .......................................[3]

(iii)

The combined resistance of the external resistor and thermistor X connected in parallel is 4.8 Ω.

Calculate the resistance of X.

resistance = ........................................ Ω [1]

(iv)

Use your answer in (b)(iii) to determine the ratio

\frac{power dissipated in thermistor X}{power dissipated in 12 Ω resistor}

ratio = .................................. [2]

(v)

The temperature of thermistor X is now decreased.

State and explain the effect, if any, of this temperature change on the total power produced by the battery.

[3]

How did you do?

Did this page help you?

1 mark

A student investigates the potential difference in a circuit. The circuit is set up as shown in Fig. 2.1.

q2-paper-5-specimen-2022-cie-ial-physics

Fig. 2.1

Two resistors P and Q are connected in series to a power supply of electromotive force (e.m.f.) E and negligible internal resistance. Resistor P has resistance P.

The potential difference V across resistor P is measured. The experiment is repeated for different values of P.

It is suggested that V and P are related by the equation

$V = (\frac{P}{P + Q}) E$

where Q is the resistance of resistor Q. The value of Q is kept constant.

A graph is plotted of $\frac{1}{V}$ on the y-axis against $\frac{1}{P}$ on the x-axis.

Determine expressions for the gradient and the y-intercept.

gradient = ............................................
y-intercept = .......................................

How did you do?

2 marks

Values of P, V and $\frac{1}{V}$ are given in Table 2.1.

Table 2.1

P / Ω	V / V	$\frac{1}{P}$ / 10^–3 Ω^–1	$\frac{1}{V}$ / V^–1
250	0.66		1.52
330	0.86		1.16
470	1.15		0.870
560	1.30		0.769
680	1.49		0.671
840	1.64		0.610

Each value of P has an uncertainty of ±10%.

Calculate and record values of $\frac{1}{P}$ / 10^–3 Ω^–1 in Table 2.1.

Include the absolute uncertainties in $\frac{1}{P}$ .

How did you do?

8 marks

(i)

Plot a graph of

\frac{1}{V}

/ V^–1 against

\frac{1}{P}

/ 10^–3 Ω^–1.

Include error bars for $\frac{1}{P}$ .

[2]

(ii)

Draw the straight line of best fit and a worst acceptable straight line on your graph. Label both lines.

[2]

(iii)

Determine the gradient of the line of best fit. Include the absolute uncertainty in your answer.

gradient = ......................................... [2]

(iv)

Determine the y-intercept of the line of best fit. Include the absolute uncertainty in your answer.

y-intercept = ......................................... [2]

How did you do?

4 marks

(i)

Using your answers to (a), (c)(iii) and (c)(iv), determine the values of E and Q. Include appropriate units.

E = ..............................................
Q = .............................................
[2]

(ii)

Determine the percentage uncertainty in E.

percentage uncertainty in E = ......................................... % [1]

(iii)

Determine the absolute uncertainty in Q.

absolute uncertainty in Q = ........................................ [1]

How did you do?

Did this page help you?

CIE AS Physics

Topic Questions

10.1 DC: Practical Circuits & Kirchhoff's Laws

	Download	View
Easy
Medium