A battery with e.m.f. $6.0\ \text{V}$ and negligible internal resistance is linked to three resistors, each having resistance $2.0\ \text{k}\Omega$, together with a thermistor, as illustrated in Fig. 9.1. The thermistor’s resistance is $2.8\ \text{k}\Omega$ at $10\,^{\circ}\text{C}$ and $1.8\ \text{k}\Omega$ at $20\,^{\circ}\text{C}$.
(a(i))[1]
Calculate the electric potential at point A.
(a(ii))[2]
Calculate the electric potential at point B for the thermistor at $10\,^{\circ}\text{C}$.
(a(iii))[1]
Calculate the electric potential at point B for the thermistor at $20\,^{\circ}\text{C}$.
(b)[4]
As shown in Fig. 9.2, points A and B from Fig. 9.1 are joined to the inputs of an ideal operational amplifier (op-amp). The thermistor is warmed from $10\,^{\circ}\text{C}$ to $20\,^{\circ}\text{C}$. State and explain how the output potential $V_{\text{OUT}}$ of the op-amp changes as the thermistor is warmed.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “= $+3.0\,\text{V}$” …