At fixed potential difference 3.0 V, a thermistor carries 0.0020 A in cool water and 0.0060 A in warm water. It is the type whose resistance falls as temperature rises.
.1
Calculate the resistance in cool water.
[2 marks]
.2
Calculate the resistance in warm water.
[2 marks]
.3
A pupil says the current tripled because the supply voltage tripled. Evaluate the statement using the data.
[2 marks]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A solenoid produces a field resembling that of a bar magnet. A compass near end X points away from X with its north-seeking end. The current is then reversed.
.1
Determine the initial polarity of X and its polarity after reversal. Explain the reasoning.
[2 marks]
.2
Compare the field inside a long solenoid with its field near an open end.
[2 marks]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A 15 Ω resistor carries a current of 0.40 A for 200 s. Its resistance remains constant.
.1
Calculate the resistor's power.
[2 marks]
.2
Calculate the energy transferred in 200 s.
[2 marks]
.3
Predict and explain the effect on power of doubling current at the same resistance.
[2 marks]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Equal hot-water bottles are wrapped in equal-thickness samples of wool, foam and foil. In 10 minutes their temperature falls are 5 °C, 3 °C and 7 °C respectively. The starting temperatures, water masses and room temperatures are the same.
Evaluate the conclusion that foam is always the best insulator. Include evidence, limitations and an improved comparison.
[6 marks]
4 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A force-extension graph is straight from the origin to force 5.0 N and extension 0.040 m. A student says the work done stretching the spring equals 5.0×0.040 J.
.1
Calculate the energy actually stored in the spring.
