Mutual Induction Investigation Kit

Quick Answer: The Mutual Induction Investigation Kit is a two-coil apparatus for studying how a changing current in one coil induces an EMF in a second, separate coil. The listing image shows a primary coil and a secondary coil mounted side by side on a board with supply terminals and an output indicator.

One Coil Driving Another

When the current in the primary coil changes, the magnetic field around it changes too, and part of that field threads through the secondary coil. The changing flux induces an EMF in the secondary even though the two coils are not electrically connected. This is mutual induction, the working principle of every transformer, wireless charger and induction coil.

With an alternating supply on the primary, the secondary produces a continuous alternating output that the indicator shows. With a battery and switch instead, a galvanometer on the secondary kicks one way when the switch closes, the other way when it opens, and stays at zero while the current is steady. That single contrast is the clearest proof that it is change, not current itself, that induces a voltage.

The mutual induction kit also supports simple investigations where the design allows: changing the spacing or alignment of the coils, or passing an iron rod through them and watching the output rise. The coil turns, the indicator type and the supply required should be confirmed when ordering.

Applications

• Demonstrating mutual induction between two separate coils
• Showing that a steady direct current induces nothing in the secondary
• Investigating how an iron core and coil alignment change the output
• Building understanding before transformer and wireless charging lessons

Specifications

Care & Handling

• Use only the low-voltage supply specified for the kit, never a direct mains connection.
• Switch off before changing connections, and keep leads tidy so the terminals are not strained.
• Allow the coils to cool if they have carried current for a long time.
• Store the board dry and flat, protecting the coil windings from knocks and scratches.

Why Choose LabEquip

Physics teachers buy this kit to bridge Faraday’s law and the transformer, since it shows induction between coils without the enclosed core of a finished transformer. LabEquip supplies it through the STEM kits range, and the Step Down Electrical Transformer Apparatus is the natural next practical. Get in touch via our contact page.

Frequently Asked Questions

What is mutual induction?

Mutual induction is the production of an EMF in one coil by a changing current in a nearby coil. The changing current creates a changing magnetic field, and the part of that field passing through the second coil induces a voltage in it.

Why does a steady direct current produce no output?

Induction needs a changing magnetic flux. A steady current gives a constant field, so the flux through the secondary does not change and no EMF is induced. Output appears only at the moments the current is switched on or off.

How does an iron core increase the effect?

Iron is easily magnetised and concentrates the magnetic field, guiding much more of the primary’s flux through the secondary. The stronger linked flux changes more with each cycle, so a larger EMF is induced.

What is the difference between mutual induction and self-induction?

In self-induction a changing current in a coil induces an EMF in that same coil, opposing the change. In mutual induction the EMF appears in a second coil. Both follow from Faraday’s and Lenz’s laws.

How is mutual induction used in a transformer?

A transformer is two coils wound on a shared iron core so that nearly all the primary’s flux passes through the secondary. The ratio of turns on the two coils then sets the ratio of output voltage to input voltage.

Why does the output change when the coils are moved apart?

Moving them apart, or turning one relative to the other, reduces how much of the primary’s field threads the secondary. Less linked flux means a smaller change of flux in the secondary and so a smaller induced EMF.

Last Updated: September 2026