Physics 9702 · AS & A Level · Electric potential

Electric potential — practice question

(a)[2]

The slew rate of an ideal operational amplifier (op-amp) is infinite. State what is meant by infinite slew rate.

(b(i))[2]

The circuit in Fig. 6.1 is intended to show whether the thermistor temperature is above or below $24^\circ\text{C}$. The operational amplifier (op-amp) is assumed to be ideal. At $24^\circ\text{C}$, the thermistor has a resistance of $1.50\,\text{k}\Omega$. Find the resistance of resistor $R$ so that the op-amp output $V_{\text{OUT}}$ switches at $24^\circ\text{C}$.

(b(ii).1)[2]

On Fig. 6.1, draw two light-emitting diodes (LEDs) so that they indicate whether the op-amp output $V_{\text{OUT}}$ is $+5\,\text{V}$ or $-5\,\text{V}$.

(b(ii).2)[3]

Label with the letter G the LED that will light when the temperature is below $24^\circ\text{C}$. Explain your answer.

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: A statement linking the input and output voltages, with no time delay

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