The transformer Flashcards – Cambridge IGCSE (9–1) Physics 0972 (Extended) (2026–2028)

What is the basic structure of a simple transformer?

Two coils of wire wound around a shared soft-iron core.

What are the roles of the primary and secondary coils in a transformer?

The primary is connected to an alternating voltage; the secondary provides the output voltage.

How does a transformer induce a voltage in its secondary coil?

Alternating current in the primary produces a changing magnetic field in the core, inducing an alternating voltage across the secondary.

What is the transformer equation relating voltage to the number of turns?

$\frac{V_{\mathrm{p}}}{V_{\mathrm{s}}}=\frac{N_{\mathrm{p}}}{N_{\mathrm{s}}}$ Here $V$ is voltage, $N$ is the number of turns, and the subscripts denote primary and secondary.

How do the coil turns and voltage change in a step-up transformer?

The secondary has more turns than the primary, and the voltage increases.

How do the coil turns and voltage change in a step-down transformer?

The secondary has fewer turns than the primary, and the voltage decreases.

Why is electricity transmitted at high voltage?

To reduce energy losses from heating transmission cables and make transmission more efficient.

For a given transmitted power, how does increasing the voltage affect the current?

It reduces the current.

How does the rate of heating in a transmission cable depend on current and resistance?

It depends on $I^2R$.

What roles do step-up and step-down transformers play in electricity transmission?

A step-up transformer raises the voltage for transmission; step-down transformers reduce it for distribution and use.