Physics 5054 · O Level · Resistance

Resistance — practice question

A student studies a thermistor with the circuit shown in Fig. 2.1.
(a)[3]

Draw a schematic of the circuit.

(b)[1]

The student takes the room temperature measurement and notes it. The result is displayed in Fig. 2.2. Record the reading $V_W$ from Fig. 2.3.

(c)[1]

The thermistor is put into the beaker of ice and water and, after a minute, the voltmeter is read once more. Record the reading $V_C$ from Fig. 2.5.

(d(i))[2]

Calculate the average change in voltage for one degree temperature change $\Delta V_{AV}$ using the equation: $\Delta V_{AV} = \dfrac{V_C - V_W}{T_W - T_C}$. State the unit of your answer.

(d(ii))[1]

Use your answer to (d)(i) to predict the voltage $V_{PB}$ across the thermistor when it is at body temperature. Body temperature is $37^{\circ}\text{C}$. You may assume that the average change in voltage for one degree temperature change $\Delta V_{AV}$ remains constant.

(d(iii))[2]

State whether the student's results show that $V_{PB}$ and $V_{AB}$ are equal within the limits of experimental accuracy. Support your response with a calculation.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: Three cells arranged in series, together with a switch, resistor and thermistor

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