1. Microwaves and radio waves are both part of the electromagnetic spectrum.
   1. How do microwaves differ from radio waves? Give one reason.
   2. Which travels faster through a vacuum?
   3. Microwaves are used by boats for radar. Radar transmitters on ships emit microwaves which are picked up by passive radar devices on smaller boats. A passive radar device is composed of an outer plastic casing and metal plates inside. What happens to the microwaves when they reach the passive radar device?
2. A family is keen to reduce the amount of energy they consume in their new home. They look up ways in which they can reduce their energy consumption. Which is the most cost-effective method over 5 years?
   

   Method of reducing energy consumption	Cost to install (£)	Annual saving on energy bill (£)
   Cavity wall installation	300	100
   Hot water tank jacket	10	30
   Upgraded central heating controls	300	70

3. A device that transforms energy always wastes energy. Explain why the total energy input of a device is always equal to the total energy output of the same device.

4. The family decide to go on holiday. They stay in a holiday cottage which uses a pre-payment electricity meter. It charges 30p per kWh. It’s cold in the evening so the family decide to switch on the 2.5 kW fire. They put £2 into the meter. How many hours will the fire last for? Use the equations below to work out your answer.

   energy transferred = power x time

   total cost = number of kilowatt-hours x cost per kilowatt-hour

5. A dolphin is swimming in the sea. The dolphin is swimming at a constant speed. The forward force, force H, is 140N. Another force, force P, is pulling the dolphin backwards
   1. What is the size of force P?
   2. If force H increases to 160N, the dolphin accelerates to a faster speed. Calculate the initial resulting force on the dolphin.
6. Despite the fact that the dolphin continues to swim with force H at 160N the resultant force on the dolphin decreases to zero. Explain why this happens?
7. Background radiation is everywhere. One natural source of background radiation is radon.
   1. What is another natural source of background radiation?
   2. X-rays are an artificial source of background radiation. What is another artificial source of radiation.

   3. When radon-222 decays it releases an alpha particle as shown in the equation below.

      222 218

      Rn ? X + alpha particle

      86 84

      How do you know that X not a radon atom?

8. 1. Having an X-ray increases the amount someone is exposed to radiation. Scientists have shown that X-rays increase the chances of someone developing cancer. They came to this conclusion by studying the medical history of two groups of people: group A and group B.
      

      Person	D	E	F	G	H	I
      X-ray record	2 arm	none	3 skull	none	none	4 hip

      Person I was put in group A. Place the other patients in either group A or group B.

   2. In order for the scientists to make a fair comparison what should they consider about the number of people in each group?
   3. What data did the scientists compare to come to their conclusion?
9. The plug below connects a television set to the mains supply.PICTURE OF A PLUG

   The plug contains a transformer. There are 4600 turns on its primary coil and 200 turns on its secondary coil. The plug is used in the mains supply and has a potential difference (p.d.) of 230 V across its primary coil.

   Use the equation below to work out the potential difference across the secondary coil.

   p.d. across primary / p.d. across secondary = number of turns on primary / number of turns on secondary

   1. Why are the coils of the transformer made of insulated wire
   2. What is the core of the transformer made of?
   3. Why is it made of this material?

ANSWERS

1. Correct answers:
   1. higher frequency, greater energy, shorter wavelengthIncorrect answers:
      different frequency, different energy, different wavelength
   2. Careful! They travel at the same speed.
   3. Correct: they pass through/are transmitted by the plastic casing and reflected by the metal plates.Incorrect: they bounce/are deflected – you must use the right term reflected
2. Don’t forget to show your markings clearly: you can receive marks for these even if your final answer is incorrectCavity wall = (100 x 5) – 300 = £200 Jacket = (10 x 5) – 30 = £20 Heating controls = (70 x 5) – 300 = £50 Answer: cavity wall
3. Correct: energy can’t be destroyed or energy is conservedIncorrect: any reference to energy being created
4. You’ll need to rearrange the equations first of all.First you need to work out the number of kilowatts per hour (energy): number of kilowatt-hours = total cost / cost per kilowatt-hour = 200 / 20 = 10# Now you need to rearrange the other equation to work out the time: time = energy / power = 10 / 2.5 = 4 Answer: 4 hours
5. 140 N
   1. 160 – 140 = 20 N
   2. 2. Correct: as the speed increases the drag force/water resistance increases until force D equals 140N/force D equals force T

      Incorrect: you can’t just say that the forces balance, you need to explain your answer

6. Answers include:
   food or drink
   rocks or building materials
   cosmic rays
7. 1. Answers include:
      nuclear power stations
      coal power stations
      nuclear accidents
      nuclear weapons testing
   2. named medical procedures in which a radioactive source is used e.g. radiotherapyAnswers not accepted:simply writing radiation
      CT scans
   3. Correct: it has a different number of protons or it has a different atomic numberIncorrect: the bottom numbers are different
8. 1. Group A: D, F, IGroup B: E, G, H
   2. Correct answer: they should be a similar number or the same number or a large number
   3. Correct answer: how many people in each group had developed cancer
9. Don’t forget to show your workings and to substitute correctlyp.d. across primary / p.d. across secondary = number of turns on primary / number of turns on secondary 230 / p.d. across secondary = 4600 / 200 230 / p.d. across secondary = 23 230 / 23 = 10 V
   1. Answers include:
      to prevent short circuiting
      to prevent the current from entering the core
      to make sure the current flows round the coilAnswers not accepted:to prevent electrocution
      mixing up electricity and current
   2. Correct: (soft) ironIncorrect: steel
   3. Correct: it can be magnetised or because it’s magneticIncorrect: it’s a conductor