Paper 1 Transformers Answers

Q	Answer	Reason
1	B	Changing flux in core induces emf in secondary.
2	B	Faraday induction requires changing flux linkage.
3	A	Ideal voltage ratio equals turns ratio.
4	A	Use $V_p{I}_p=V_s{I}_s$.
5	A	More secondary turns gives higher secondary voltage.
6	B	Power is conserved ideally.
7	B	They are magnetically coupled, not conductively connected.
8	A	Core provides low-reluctance flux path.
9	A	Thin insulated laminations limit circulating currents.
10	A	$I^{2}R$ heating in windings.
11	A	Soft iron has low hysteresis loss.
12	A	Definition.
13	A	For fixed $P$, higher $V$ gives lower $I$.
14	A	Joule heating.
15	A	Only switching transient occurs.
16	A	Standard convention.
17	A	Leakage is incomplete magnetic coupling.
18	A	Secondary has fewer turns and lower voltage.
19	A	Losses make efficiency below 100%.
20	A	Laminations interrupt eddy-current paths.