| Date | May 2015 | Marks available | 1 | Reference code | 15M.2.HL.TZ1.3 |
| Level | Higher level | Paper | Paper 2 | Time zone | Time zone 1 |
| Command term | Define | Question number | 3 | Adapted from | N/A |
Question
This question is about a thermistor circuit.
The circuit shows a negative temperature coefficient (NTC) thermistor X and a 100 kΩ fixed resistor R connected across a battery.
The battery has an electromotive force (emf) of 12.0 V and negligible internal resistance.
Define electromotive force (emf).
The graph below shows the variation with temperature T of the resistance RX of the thermistor.
(i) Determine the temperature of X when the potential difference across R is 4.5 V.
(ii) State the range of temperatures for which the change in the resistance of the thermistor is most sensitive to changes in temperature.
(iii) State and explain the effect of a decrease in temperature on the ratio \(\frac{{{\rm{voltage across X}}}}{{{\rm{voltage across R}}}}\).
Markscheme
the work done per unit charge in moving a quantity of charge completely around a circuit / the power delivered per unit current / work done per unit charge made available by a source;
