Edexcel GCSE Combined Science: Physics: Magnetism and Electromagnetism

A scrapyard uses an electromagnet on a crane to lift and move large pieces of iron and steel. An electromagnet is made by winding a coil of wire (a solenoid) around an iron core and passing a current through it.

Explain how the electromagnet works, why an electromagnet is more suitable than a permanent magnet for this job, and describe how the strength of the electromagnet could be increased. (6 marks)

(This question is targeted at Higher tier.)

A straight wire of length 0.25 m carries a current of 4.0 A. The wire is placed at right angles to a uniform magnetic field of magnetic flux density 0.30 T. Because of the motor effect, the wire experiences a force.

(a) Calculate the force acting on the wire. Use the equation $F = BIl$F=BIl. Show your working and give the unit. (3 marks)

(b) State the name of the rule used to find the direction of the force on the wire. (1 mark)

Magnets can be classified as permanent magnets or induced magnets.

(a) State one difference between a permanent magnet and an induced magnet. (1 mark)

(b) State whether the force between a magnet and a nearby piece of unmagnetised iron is attraction, repulsion, or both are possible, and briefly justify your answer. (2 marks)

A current flows through a long straight wire, producing a magnetic field around it.

(a) Describe the shape and pattern of the magnetic field around a long straight current-carrying wire. (2 marks)

(b) State one way in which the magnetic field around the wire could be made stronger. (1 mark)

A solenoid is a coil of wire that carries a current. When a current flows, the solenoid produces a magnetic field.

Describe the magnetic field produced inside and around a current-carrying solenoid. (2 marks)

The unit of magnetic flux density is named after a scientist.

Give the name of the unit of magnetic flux density, and its symbol. (1 mark)