Use the idea of a conductor cutting magnetic field lines to explain how a current is caused by induced e.m.f. in a bicycle generator .

In a bicycle generator, a permanent magnet rotates inside a fixed coil of wire .

The coil in Figure, is rotating in a uniform magnetic field. Predict the direction of the current caused by induced e.m.f. in sections $AB$ and $CD$. State which terminal, $X$ or $Y$, will become positive.

A coil rotating in a uniform magnetic field.

In an experiment to investigate the factors that affect the magnitude of an induced e.m.f., a student moves a wire back and forth between two magnets, as shown in Figure ,State why the e.m. f. generated in this way is almost zero.

A wire is moved horizontally in a horizontal magnetic field.

In the type of generator found in a power station, a large electromagnet is made to rotate inside a fixed coil. An e.m.f. of 25 kV is induced; this is an alternating voltage of frequency $50Hz.$

(a) State the factor that determines the frequency.

In the type of generator found in a power station, a large electromagnet is made to rotate inside a fixed coil. An $e.m.f.$of$25kV$ is induced; this is an alternating voltage of frequency $50Hz.$

(b) Suggest the factors that you think would affect the magnitude of the induced $e.m.f.$

A solenoid has diameter $5.0 cm$ length $25 cm$and $200$ turns of wire. A current of $2.0A$ creates a uniform magnetic field of flux density $2.0\times {10}^{-5}$$T$ through the core of this solenoid.

A solenoid.

(a) Calculate the magnetic flux linkage for this solenoid.