This diagram shows a piece of silicon of width $32 \mathrm{mm}$ and length $36 \mathrm{mm}$. The resistance of the silicon between the points $\mathrm{P}$ and $\mathrm{Q}$ is $1.1\mathrm{M}\Omega$. Silicon has a resistivity of $2.3\times {10}^3\Omega \mathrm{m}$.

Calculate the thickness of the piece of silicon.

This diagram shows a piece of silicon of width $32 \mathrm{mm}$ and length $36 \mathrm{mm}$. The resistance of the silicon between the points $\mathrm{P}$ and $\mathrm{Q}$ is $1.1\mathrm{M}\Omega$. Silicon has a resistivity of $2.3\times {10}^3\Omega \mathrm{m}$.

Calculate the current that would pass through the silicon if a potential difference of $12\mathrm{V}$ were applied across $\mathrm{P} \& \mathrm{Q}$.

This diagram shows a piece of silicon of width $32 \mathrm{mm}$ and length $36 \mathrm{mm}$. The resistance of the silicon between the points $\mathrm{P}$ and $\mathrm{Q}$ is $1.1\mathrm{M}\Omega$. Silicon has a resistivity of $2.3\times {10}^3\Omega \mathrm{m}$.

Describe how the current would change if it were large enough to cause the silicon to become significantly warmer.

A student is investigating the properties of a semiconducting diode. This diagram shows the circuit she builds.

Sketch a graph to show how the current in the diode would vary as the voltage across it is increased from $0 \mathrm{V}$ to $1.0 \mathrm{V}$.

A student is investigating the properties of a semiconducting diode. This diagram shows the circuit she builds.

The supply is now connected in the reverse direction and once more the potential difference across the diode is increased from $0 \mathrm{V}$ to $1.0 \mathrm{V}$. Complete the $I-V$, graph.

A student is investigating the properties of a semiconducting diode. This diagram shows the circuit she builds.

Suggest why the safety resistor is required.

A student is investigating the properties of a semiconducting diode. This diagram shows the circuit she builds.

When the potential difference across the safety resistor is $1.4 \mathrm{V}$, the current in it is $20 \mathrm{mA}$. Calculate the resistance of the safety resistor.

(a) Explain what is meant by an ohmic conductor.

Sketch a graph of resistance $R$ against voltage $V$ for a wire of pure iron kept at constant temperature. Label this line $X$.