Physics 9702 · AS & A Level · Characteristics of alternating currents

Characteristics of alternating currents — practice question

Fig. 9.1 shows an amplifier circuit that uses an operational amplifier (op-amp).
(a(i))[1]

State the name of this amplifier circuit.

(a(ii))[1]

State the gain $G$ in terms of the resistances $R_1$ and $R_2$.

(b(i))[2]

Here $R_1$ has a value of $820\,\Omega$. The resistor with resistance $R_2$ is replaced by a light-dependent resistor (LDR). The input potential difference $V_{\text{IN}}$ is $15\,\text{mV}$. Calculate the output potential difference $V_{\text{OUT}}$ for an LDR resistance of $100\,\Omega$ (the LDR is in sunlight).

(b(ii))[1]

Here $R_1$ has a value of $820\,\Omega$. The resistor with resistance $R_2$ is replaced by a light-dependent resistor (LDR). The input potential difference $V_{\text{IN}}$ is $15\,\text{mV}$. Calculate the output potential difference $V_{\text{OUT}}$ for an LDR resistance of $1.0\,\text{M}\Omega$ (the LDR is in darkness).

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