Physics 9702 · AS & A Level · Rectification and smoothing

Rectification and smoothing — practice question

(a)[2]

An ideal operational amplifier (op-amp) is described as having an infinite slew rate. Explain what infinite slew rate means.

(b(i))[2]

Fig. 6.1 shows a circuit that is intended to indicate whether the thermistor temperature is above or below $24\,^{\circ}\text{C}$. The operational amplifier (op-amp) is taken 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, sketch two light-emitting diodes (LEDs) connected so that they indicate whether the op-amp output $V_{\text{OUT}}$ is either $+5\,\text{V}$ or $-5\,\text{V}$.

(b(ii).2)[3]

Label with the letter G the LED that glows when the temperature is below $24\,^{\circ}\text{C}$. Explain your working.

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: The input and output voltages are linked with no time delay between them

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