Physics 9702 · AS & A Level · Electric potential

Electric potential — practice question

An operational amplifier (op-amp) is employed in the comparator circuit shown in Fig. 10.1.
(a(i))[1]

Show that the potential at the inverting input of the op-amp is $+1.0\,\text{V}$.

(a(ii))[4]

Explain why the potential difference across resistor $R$ is $+5\,\text{V}$ when $V_{\text{IN}}$ is greater than $1.0\,\text{V}$ and becomes zero when $V_{\text{IN}}$ is less than $1.0\,\text{V}$. $V_{\text{IN}} > 1.0\,\text{V}$: $V_{\text{IN}} < 1.0\,\text{V}$:

(b(i))[2]

On the axes in Fig. 10.2, plot how the output potential $V_{\text{OUT}}$ varies with time $t$.

(b(ii))[1]

Suggest a use for this type of circuit.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: The potential divider gives $+1.0\,\mathrm{V}$

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