C-Core and Coil Bundle

Build a working transformer and prove the turns ratio law yourself

The C-Core and Coils Bundle lets students build a working transformer from scratch: a laminated steel C-core plus five coils of different turn counts, each with a center tap that unlocks a second and third turn value. Pair any two coils on the core, one carrying alternating current as the primary, one picking up an induced voltage as the secondary, and students see directly how the ratio of turns between two coils sets the ratio of voltages between them. It's the same principle behind every transformer in the power grid, in a phone charger, or in a doorbell.

The relationship is simple: Vs/Vp = Ns/Np. More turns on the secondary steps voltage up, fewer steps it down.

Requires, but does not include, a low-voltage AC power source and banana plug leads to connect the coils, meter, and power source. Never connect the primary directly to a wall outlet; use only a classroom-rated low-voltage AC source.

Why Teachers Love It

• Five Coils, Ten Turn Values – Each coil's center tap unlocks a second and third turn count, so five coils give ten configurations for testing turns ratio against voltage.

• Built-In Activity Progression – From directly confirming Vs/Vp = Ns/Np, to isolating turns as a single variable, to designing a transformer that hits a target voltage, the bundle scales from a first demo to an applied design challenge.

• Build It, Then Measure It – Students don't model a transformer's behavior on paper; they wind it, power it, and check whether the actual voltage matches the predicted turns ratio.