The operation of a transformer (A-level only) Flashcards – AQA A-level Physics (7408)

What are eddy currents?

Circulating currents induced within a conductor when the magnetic flux through paths in it changes.

What magnetic effect do eddy currents have on the change that induces them?

They produce magnetic effects that oppose the change.

Why do eddy currents dissipate energy as thermal energy?

Because the conductor has resistance.

How do laminations reduce eddy-current heating in a transformer core?

Thin conducting laminations separated by insulating layers restrict the paths available to eddy currents.

Why does transmitting a given real power at higher voltage reduce heating losses in transmission lines?

Higher voltage allows a lower current, which reduces the line’s heating loss.

What equation gives the heating loss in a transmission line, and what resistance does it use?

$P_{\text{loss}}=I^2R$

Here, $R$ is the total resistance of the conducting transmission path carrying current $I$.

How can transmission current be calculated from real power $P$ and voltage $V$ when their product gives real power?

$I=\frac{P}{V}$

What role do transformers play in high-voltage power transmission?

They raise the voltage for transmission and reduce it again for use.