6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Learn this properly: Poles and Magnetic FieldsA simple electromagnet is made by winding a coil of insulated wire around an iron core and connecting it to a battery. When the current is switched on, the device behaves as a magnet; when the current is switched off, it loses almost all of its magnetism.
Describe and explain how this electromagnet works, and explain two ways in which the strength of the electromagnet could be increased. Refer to the magnetic field and the iron core in your answer. (6 marks)
A straight horizontal wire of length 0.050 m lies at right angles to a magnetic field of flux density 0.20 T. A current of 1.5 A flows through the wire. (This question uses the motor effect — Higher-tier content.)
(a) Calculate the force on the wire. Use F=BIl. Show your working and give the unit. (2 marks)
(b) State two changes that would increase the size of this force. (2 marks)
A transformer has 200 turns on its primary coil and 1000 turns on its secondary coil. The input (primary) potential difference is 12 V. (This question uses transformers — Higher-tier content.)
(a) Calculate the output (secondary) potential difference. Use VsVp=nsnp. Show your working and give the unit. (2 marks)
(b) State whether this is a step-up or a step-down transformer, and give a reason. (1 mark)
A bar magnet is pushed into a coil of wire that is connected to a sensitive voltmeter. A potential difference is induced while the magnet moves. (This question uses the generator effect — Higher-tier content.)
(a) State what happens to the induced potential difference if the magnet is held stationary inside the coil. (1 mark)
(b) State two ways to increase the size of the induced potential difference. (2 marks)
Magnets can be classified as permanent magnets or induced magnets.
Explain the difference between a permanent magnet and an induced magnet, and state what happens to an induced magnet when it is removed from a magnetic field. (2 marks)
Two north poles of two bar magnets are brought close together.
State whether the magnets will attract or repel each other. (1 mark)