An ideal transformer has NpN_{\text{p}}Np turns on its primary coil and NsN_{\text{s}}Ns turns on its secondary coil. The current in the primary coil is IpI_{\text{p}}Ip and the current in the secondary coil is IsI_{\text{s}}Is.
What is the relationship between these four quantities?
IpIs=NpNs\frac{I_{\text{p}}}{I_{\text{s}}} = \frac{N_{\text{p}}}{N_{\text{s}}}IsIp=NsNp
IpIs=NsNp\frac{I_{\text{p}}}{I_{\text{s}}} = \frac{N_{\text{s}}}{N_{\text{p}}}IsIp=NpNs
Ip×Is=Np×NsI_{\text{p}} \times I_{\text{s}} = N_{\text{p}} \times N_{\text{s}}Ip×Is=Np×Ns
IpIs=Np×Ns\frac{I_{\text{p}}}{I_{\text{s}}} = N_{\text{p}} \times N_{\text{s}}IsIp=Np×Ns
275 exam-style questions on CIE IGCSE Physics 4.5 Electromagnetic effects, covering 4.5.1a Electromagnetic induction, 4.5.1b Direction of an induced e.m.f., 4.5.2 The a.c. generator, 4.5.3a Magnetic effect of a current and its applications, 4.5.3b Strength and direction of the field around wires and solenoids, 4.5.4a Force on a current-carrying conductor, 4.5.4b Force on beams of charged particles, 4.5.5 The d.c. motor, 4.5.6a Construction and operation of a transformer, 4.5.6b Turns ratio and current in a transformer, and 4.5.6c High-voltage transmission of electricity. Each one has a worked solution and a mark scheme showing where the marks go.