By Susan Kristoff
Updated Mar 24, 2022
An electromagnet generates a magnetic field by running electric current through a coil of wire wrapped around a ferromagnetic core. The pull strength of the magnet is directly proportional to the current flowing through the coil. Measuring that pull force is simple and can be performed with a few common tools.
Hang the electromagnet from a hook or stand so that it hangs freely.
Connect the electromagnet to a battery or a low‑voltage power supply. If you’re using a power supply, switch it on.
Attach a spring scale to the electromagnet so that only the magnetic attraction holds the scale. The scale should cling to the magnet without any other support.
Gently add weights to the hook of the spring scale. Add them slowly to avoid the sudden drop of a weight that could dislodge the scale. Record the weight displayed on the scale.
Continue adding weights until the spring scale detaches from the magnet. Note the total weight that the magnet held before the scale fell.
Remove the weights and repeat steps 3–5 two more times to obtain three independent measurements.
Calculate the average of the three recorded weights by adding them together and dividing by three. This average represents the electromagnet’s pulling force.
Use a spring scale to measure the pull force of an electromagnet. Vary the current on a power supply and repeat the test to see how current influences strength.
Only use batteries or a low‑voltage power supply for this test. Higher voltages can cause fires or electrocution if handled improperly.
