Electricity and Magnetism

Moving an electromagnet

Practical Activity for 14-16 PRACTICAL PHYISCS

Class practical

An electromagnet is now used instead of a permanent magnet with similar effects. This is to be expected, but it is satisfying to see in action.

Apparatus and Materials

  • Copper wire, insulated with bare ends, 200 cm
  • C-cores, laminated iron, 2
  • Cell, 1.5 V in holder
  • Galvanometer, sensitive to e.g. 3.5–0–3.5 mA., 10 ohm resistance (see note below)

Please note: Strictly speaking, we generate e.m.f. but frequently measure the current through the load resistor (i.e. the wire) using a galvanometer (not an ammeter).

Health & Safety and Technical Notes

If a zinc chloride cell is used, it will polarize in 60 s or less and must be left overnight to recover.

If an alkaline manganese cell is used, there is a danger of the cell overheating with a risk of explosion: complete the circuit for 30 s or less.

If a re-chargeable cell (NiCd) is used, the wire will get very hot and the cell will be discharged in a few minutes: do the experiment as quickly as possible.

Read our standard health & safety guidance

It is possible to use a low-voltage power supply instead of the 1.5 V cell, but any ripple on the d.c. output can lead to confusion.


  1. Wind a coil of roughly 20 turns on one arm of a C-core.
  2. Connect the coil by long leads to a galvanometer. This is Coil 1.
  3. Wind a coil of 10 turns on one arm of the second C-core.
  4. Connect this coil to the 1.5 V cell. This is Coil 2.
  5. Coil 2 becomes an electromagnet. Bring it up to Coil 1, as shown. Observe the effect.
  6. Take Coil 2 away again. Observe the effect.
  7. Find out how the deflection on the galvanometer changes if the current in Coil 2 is reversed.
  8. Investigate the factors which affect the deflection on the galvanometer.

Teaching Notes

Students will find that:

  • There is only a current when Coils 1 and 2 are moving relative to each other;
  • Reversing the movement of Coil 2 reverses the deflection on the galvanometer;
  • Reversing the current of Coil 2 reverses the deflection on the galvanometer;
  • Faster movement results in a bigger deflection.

This experiment was safety-tested in January 2005

Limit Less Campaign

Support our manifesto for change

The IOP wants to support young people to fulfil their potential by doing physics. Please sign the manifesto today so that we can show our politicians there is widespread support for improving equity and inclusion across the education sector.

Sign today