An electric kettle has an input power of 2000 W. The useful power output, heating the water, is 1800 W.
.1
Calculate the efficiency of the kettle.
[2 marks]
.2
Calculate the power wasted by the kettle.
[1 mark]
.3
Give one way energy is wasted by the kettle.
[1 mark]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A country needs a new power station. It could build a hydroelectric power station in a mountain valley or a gas-fired power station near a town.
Comparison of two power stations. Hydroelectric: fuel cost none; carbon dioxide when generating none; start-up time about 1 minute; building cost very high; needs a flooded valley. Gas-fired: fuel cost high; carbon dioxide when generating yes; start-up time about 15 minutes; building cost medium; can be built near towns.
Feature
Hydroelectric
Gas-fired
Fuel cost
None
High
Carbon dioxide when generating
None
Yes
Start-up time
About 1 minute
About 15 minutes
Building cost
Very high
Medium
Site
Needs a flooded valley
Can be built near towns
Evaluate the two options. Use information from the table and your own knowledge.
[6 marks]
8 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Hospitals use X-rays to form images of the inside of the body. A CT scan uses X-rays from many directions. The table shows some typical radiation doses.
Typical radiation dose in millisieverts: one chest X-ray 0.02; one CT scan of the chest 7.0; background radiation in one year, UK average, 2.7.
Source of radiation
Typical dose in mSv
One chest X-ray
0.02
One CT scan of the chest
7.0
Background radiation in one year (UK average)
2.7
.1
Calculate how many chest X-rays give the same dose as one CT scan of the chest.
[2 marks]
.2
Calculate the dose from one CT scan of the chest as a percentage of the yearly background dose.
[2 marks]
.3
A patient has had a cough for several months. Evaluate the use of a CT scan of the chest to find the cause.
[3 marks]
.4
Give one harmful effect of ultraviolet radiation on the human body.
[1 mark]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Radium-226 decays by emitting an alpha particle:
88226Ra→ZARn+24He
.1
Determine the mass number A of the radon nucleus.
[1 mark]
.2
Determine the atomic number Z of the radon nucleus.
[1 mark]
.3
Strontium-90 decays by beta emission. Describe what happens in the nucleus during beta decay.
[2 marks]
7 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Waves travel across a pond. A floating leaf moves up and down 5 times in 2.0 s. The distance between neighbouring crests is 0.40 m.
.1
Calculate the frequency of the waves.
[1 mark]
.2
Calculate the speed of the waves.
[2 marks]
.3
Calculate the period of the waves.
[2 marks]
.4
The leaf moves up and down but does not travel across the pond with the waves.
Explain what this shows about the waves.
