A battery with e.m.f. $6.0\ \text{V}$ and negligible internal resistance is joined to three resistors, each of resistance $2.0\ \text{k}\Omega$, together with a thermistor, as shown in Fig. 9.1. The thermistor has a resistance of $2.8\ \text{k}\Omega$ at $10^{\circ}\text{C}$ and a resistance of $1.8\ \text{k}\Omega$ at $20^{\circ}\text{C}$.
(a(i))[1]
Calculate the electric potential at point A.
(a(ii))[2]
Calculate the potential at point B when the thermistor is at $10^{\circ}\text{C}$.
(a(iii))[1]
Calculate the potential at point B when the thermistor is at $20^{\circ}\text{C}$.
(b)[4]
In Fig. 9.2, the inputs of an ideal operational amplifier (op-amp) are connected to points A and B from Fig. 9.1. The thermistor is warmed from $10^{\circ}\text{C}$ to $20^{\circ}\text{C}$. State and explain how the op-amp output potential $V_{\text{OUT}}$ 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: “The value is $+3.0\ \text{V}$.” …