Physics 9702 · AS & A Level · Electric potential

Electric potential — practice question

Suggest one electrical sensing device for each situation that could be used to track changes in
(a(i))[1]

light intensity.

(a(ii))[1]

the width of a crack in a welded joint.

(a(iii))[1]

the intensity of an ultrasound beam.

(b)

A student sets up the circuit in Fig. 9.1 to detect temperature changes over the range $0\,^{\circ}\text{C}$ to $100\,^{\circ}\text{C}$. The thermistor has resistance $R_T$ and the resistor has resistance $R$. The student observes the potential difference $V_{\text{OUT}}$. State and explain

(b(i))[3]

whether $V_{\text{OUT}}$ rises or falls as the thermistor becomes hotter.

(b(ii))[2]

whether the change in $V_{\text{OUT}}$ is linear with the change in the thermistor’s temperature.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: light-dependent resistor (LDR)

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