IB Physics SL B.5.13 Series and Parallel Circuits Question Bank

Practise IB Physics SL B.5.13 by reducing series and parallel networks, assigning current and potential difference correctly, and predicting branch changes.

Exam points

Reduce mixed resistor networks using series sums and reciprocal parallel resistance before finding current.
Use equal series current and equal parallel potential difference to determine branch readings.
Predict how a switch or added branch changes total resistance, current and lamp power.

[Maximum number: 4]

This question is in two parts. Part 1 is about a thermistor circuit. Part 2 is about vibrations and waves.
Part 1 Thermistor circuit
The circuit shows a negative temperature coefficient (NTC) thermistor X and a $100 \mathrm{k} \Omega$ fixed resistor R connected across a battery.

Figure for Question B.5.13—Series and parallel circuits question 1 — IB Physics SL

The battery has an electromotive force (emf) of 12.0 V and negligible internal resistance.

The graph below shows the variation with temperature T of the resistance $R_{\mathrm{x}}$ of the thermistor.

Determine the temperature of X when the potential difference across R is 4.5 V .

$V_X=7.5\,\mathrm{V}$ $I=\frac{4.5\,\mathrm{V}}{100\times10^3\,\Omega}=4.5\times10^{-5}\,\mathrm{A}$ $R_X=\frac{7.5\,\mathrm{V}}{4.5\times10^{-5}\,\mathrm{A}}=1.67\times10^5\,\Omega$ $T=-37\text{ to }-38\,^{\circ}\mathrm{C}$

Alternatively, use the potential-divider relation V_X/V_R=R_X/R_R or the equivalent resistance calculation.

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B.5.13—Series and parallel circuits question 1