The diagram shows a simple a.c. generator.

Suggest two ways in which the e.m.f. could be increased.

A coil $P$ is joined to a battery and a switch $S$. A similar coil $Q$ is joined to a sensitive centre-zero millivoltmeter $G$.

$P$ and $Q$ are placed end to end, as shown in the diagram.

Describe what is seen happening to the reading of $G$: as switch $S$ is closed.

A coil $P$ is joined to a battery and a switch $S$. A similar coil $Q$ is joined to a sensitive centre-zero millivoltmeter $G$.

$P$ and $Q$ are placed end to end, as shown in the diagram.

Describe what is seen happening to the reading of $G$: as switch $S$ is closed and opened again.

A coil $P$ is joined to a battery and a switch $S$. A similar coil $Q$ is joined to a sensitive centre-zero millivoltmeter $G$.

$P$ and $Q$ are placed end to end, as shown in the diagram.

A soft iron bar, as long as the combined lengths of $P$ and $Q$, is placed inside $P$ and $Q$. State what difference this makes to what is observed on $G$ as $S$ is closed.

A coil $P$ is joined to a battery and a switch $S$. A similar coil $Q$ is joined to a sensitive centre-zero millivoltmeter $G$.

$P$ and $Q$ are placed end to end, as shown in the diagram.

A soft iron bar, as long as the combined lengths of $P$ and $Q$, is placed inside $P$ and $Q$. Then the bar is removed and the battery is changed for one with a smaller e.m.f. State what difference this makes to which is observed on $G$ as $S$ is closed.

A coil $P$ is joined to a battery and a switch $S$. A similar coil $Q$ is joined to a sensitive centre-zero millivoltmeter $G$.

$P$ and $Q$ are placed end to end, as shown in the diagram.

The battery is replaced by an a.c. power supply of frequency $50$ cycles per second, and then $S$ is closed. Describe what is seen on $G$.

A coil is wound on a cylindrical cardboard tube and connected to a sensitive centre-zero millivoltmeter. The diagram shows the situation involving the coil and a magnet.

Describe what, if anything, is seen happening on the millivoltmeter.