Physics 9702 · AS & A Level · Rectification and smoothing

Rectification and smoothing — practice question

(a(i))[1]

An ideal operational amplifier (op-amp) is described by infinite bandwidth and infinite slew rate. Explain what is meant by infinite bandwidth.

(a(ii))[1]

Explain the meaning of infinite slew rate.

(b(i))[1]

An ideal op-amp is included in the circuit of Fig. 8.1. Determine the resistance $R_T$ of the thermistor $T$ for which the output potential difference $V_{\text{OUT}}$ is zero.

(b(ii))[2]

As the thermistor is heated slowly, its resistance drops from $1.5R_T$ to $0.5R_T$. On Fig. 8.2, draw a line to indicate how the output potential difference $V_{\text{OUT}}$ varies with the thermistor resistance.

(b(iii))[2]

On Fig. 8.1, draw the symbol for a light-emitting diode (LED) at the circuit output so that it emits light when the thermistor resistance is less than $R_T$.

(c(ii))[2]

As the thermistor is heated slowly, its resistance falls from $1.5R_T$ to $0.5R_T$. On Fig. 8.2, draw a line to show how the output potential difference $V_{\text{OUT}}$ varies with thermistor resistance.

(c(iii))[2]

On Fig. 8.1, draw the symbol for a light-emitting diode (LED) at the circuit output so that it emits light when the thermistor resistance is less than $R_T$.

Worked solution & mark scheme

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