Electromagnetism test with answers for GCSE physics (free PDF download)

Quick answer: Electromagnetism links electricity and magnetism: a current produces a magnetic field, a current-carrying wire in a field feels a force F = B I L, and a changing magnetic field induces a voltage. This Physics 9-10 test on electromagnetism has 8 questions worth 20 marks, to do in 45 minutes: field lines, force on a wire and increasing the force. The mark scheme is on a separate page; free printable PDF.

This test has 8 questions worth 20 marks. Show your working for every calculation and give units. Explanations should use the correct scientific words such as field, induced and current. You have 45 minutes.

Level: Physics grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: HS-PS2-5, GCSE P7

Time: 45 minutes · 8 questions · Total: 20 marks · Calculator allowed

Contents

Question 1 Field lines (2 marks)

State two properties of magnetic field lines around a bar magnet.

Question 2 Force on a wire (3 marks)

A wire of length 0.080 m carries a current of 3.0 A at right angles to a magnetic field of 0.25 T.

Write down the equation, substitute the values and calculate the force on the wire.

Question 3 Increasing the force (2 marks)

State two ways to increase the force on a current-carrying wire in a magnetic field.

Question 4 Transformer voltage (3 marks)

The transformer in the figure has 500 turns on the primary coil and 50 turns on the secondary coil. The primary voltage is 230 V.

Transformer: two coils on a laminated iron core. The primary coil is on the left, the secondary on the right.

Calculate the secondary voltage. (2 marks)
State whether it is a step-up or a step-down transformer. (1 mark)

Question 5 Transformer power (3 marks)

The secondary of the transformer in the previous question supplies a current of 2.0 A at 23 V. Assume the transformer is 100 % efficient.

Calculate the output power and the current in the primary coil.

Question 6 How a generator works (3 marks)

Explain how a simple generator produces an alternating voltage when its coil is spun in a magnetic field.

Question 7 Direct current (2 marks)

Explain why a transformer does not work when it is connected to a battery.

Question 8 Electromagnet core (2 marks)

A coil of wire carrying a current is wound round a soft iron rod. Explain why this is a stronger magnet than the coil on its own.

Direction of field lines outside a magnet? — North pole to south pole.

Unit of magnetic field strength? — Tesla (T).

Motor effect force equation? — F = B I L.

Which hand gives force direction on a wire? — Fleming's left hand.

Force on a wire parallel to the field? — Zero.

Three ways to strengthen an electromagnet? — More current, more turns, soft iron core.

When is a voltage induced in a coil? — When the magnetic field through it changes.

Transformer turns equation? — Vp ÷ Vs = Np ÷ Ns.

Power in an ideal transformer? — Vp Ip = Vs Is.

Why can a transformer not use d.c.? — A steady field induces no voltage.