(a)[2]
State two characteristics of an ideal operational amplifier (op-amp).
(b)[1]
Fig. 7.1 presents a circuit containing an ideal op-amp together with two identical resistors $R$. State what components $X$ and $Y$ are called.
(c(i))[2]
Explain why the op-amp in Fig. 7.1 can have only two output states.
(c(ii))[1]
State the name of the op-amp circuit type in which the op-amp behaves as in (c)(i).
(c(iii))[2]
Describe the environmental condition under which the lamp $L$ in Fig. 7.1 will light.
(c(iv))[1]
Suggest what the variable resistor $V$ is for in the circuit.