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]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A pure liquid cools at a steady rate of energy loss. Its temperature falls from 60 °C to 40 °C in 4 minutes, stays at 40 °C for 6 minutes, then falls below 40 °C.
024681012203040506070Time (min)Temperature (°C)
.1
Calculate the average rate of temperature decrease during the first 4 minutes, in °C per minute.
[2 marks]
.2
Explain the horizontal section and the fall afterwards on the temperature-time graph.
[3 marks]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A detector registers 96 counts per minute of background radiation. With a source present it registers 896 counts per minute initially and 496 counts per minute after 12 minutes.
.1
Calculate the initial corrected detected count rate in min−1 (counts per minute).
[2 marks]
.2
Determine the half-life in minutes.
[2 marks]
.3
Explain why the background must be subtracted before comparing the rates.
[2 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.
[2 marks]
.2
Explain the error in the student's reasoning.
[2 marks]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A car has thinking distance 10 m and braking distance 18 m on a dry road. On a wet road at the same initial speed, its thinking distance is still 10 m and braking distance is 30 m.
.1
Calculate the percentage increase in total stopping distance on the wet road.
[3 marks]
.2
Explain why wet conditions increase braking distance in this comparison.
