Fig. 1 shows a technician testing an electromagnet used to sort steel hooks from aluminium parts on a conveyor. The coil is wound around a soft-iron rod. Th...
Question 1 Report
Fig. 1 shows a technician testing an electromagnet used to sort steel hooks from aluminium parts on a conveyor. The coil is wound around a soft-iron rod. The technician closes the switch for a short time, so current flows in the wire and the hooks are lifted into a collection box.
(a) State what happens to the steel hooks when the switch is closed. [2]
(b) Explain why increasing the current in the coil makes the electromagnet stronger. [2]
(c) Describe two changes the technician could make to increase the strength of the electromagnet without changing the cell voltage. [2]
(d) State why the technician opens the switch after the hooks are above the collection box. [2]
Answer Details
(a) When the switch is closed, current flows in the coil and produces a magnetic field. The steel hooks are attracted to, and lifted by, the electromagnet. [2]
(b) Increasing the current produces a stronger magnetic field around the coil. This magnetises the soft-iron rod more strongly, so the electromagnet becomes stronger. [2]
(c) Two ways to increase strength without changing the cell voltage are any two of: use more turns of wire on the coil, use lower-resistance wire to increase current, or use a larger soft-iron core. [2]
(d) Opening the switch stops the current, so the soft-iron core loses its electromagnetism. The hooks are then released and fall into the collection box. [2]
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