CAIE A-Level Physics AS 10.3 Potential Dividers Questions

Practise calculating potential-divider outputs, using potentiometers and null methods, and predicting sensor-controlled voltages from thermistor or LDR resistance changes.

Exam points

calculate and interpret potential-divider output p.d. and resistor ratios
use potentiometers and galvanometer null methods to compare potential differences
apply thermistor and LDR resistance changes in potential-divider circuits to predict sensor-dependent output

Covered syllabus points

10.3.1—The principle of a potential divider circuit 10.3.2—The principle of the potentiometer as a means of comparing potential 10.3.3—The use of a galvanometer in null methods 10.3.4—The use of thermistors and light-dependent resistors in potential dividers

[Maximum number: 1]

A potential divider consists of two resistors of resistances $R_{1}$ and $R_{2}$ connected in series across a source of potential difference (p.d.) $V_{\text {in }}$ . The p.d. across $R_{1}$ is $V_{\text {out }}$ .

Figure for Question 1 — CAIE A-Level Physics AS

Which changes to $R_{1}$ and $R_{2}$ will increase the value of $V_{\text {out }}$ ?

$R_{1}$

$R_{2}$

doubled

halved

doubled

halved

[Maximum number: 1]

The diagram shows a potentiometer circuit used to compare the electromotive forces (e.m.f.), $E_{1}$ and $E_{2}$ , of two cells.

XY is a uniform resistance wire. The fixed resistor has resistance R.
A sliding contact is moved along the wire XY . When the sliding contact is at position P , the galvanometer reads zero.

Figure for Question 2 — CAIE A-Level Physics AS

The circuit is changed so that the galvanometer reads zero when the sliding contact is at a new position to the left of P.

Which change could have been made to the circuit?

The wire X Y was replaced with one of lower resistance.

$E_{2}$ was increased.

$E_{1}$ was decreased.

R was decreased.

[Maximum number: 1]

In the circuit shown, a battery of negligible internal resistance is connected in series with a pair of fixed resistors $\mathrm{R}_{1}$ and $\mathrm{R}_{2}$ .

Figure for Question 3 — CAIE A-Level Physics AS

The circuit is to be used to test whether the electromotive force (e.m.f.) of a particular cell is 1.5 V . The cell is connected between terminals X and Y in parallel with $R_{2}$ and in series with a galvanometer.

Which statement about the test is correct?

Any non-zero reading on the galvanometer means the cell has an e.m.f. of 1.5 V .

The battery does not need to have an e.m.f. of 6.0 V .

The cell may be connected either way round between X and Y .

The galvanometer does not need a scale calibrated in amperes.

All question bank results loaded

Covered syllabus points

Question 1

Question 2

Question 3