Describe the difference between the conduction processes in copper and in silicon, a semiconductor.

 

Explain why the resistance of a metallic conductor increases with temperature while that of a semiconductor decreases.

A nichrome wire has a length of $1.5m$ and a cross-sectional area of$0.0080m{m}^2.$. The resistivity of nichrome is $1.30\times {10}^{-8}nm.$

Calculate the resistance of the wire.

A nichrome wire has a length of $1.5m$ and a cross-sectional area of$0.0080m{m}^2.$. The resistivity of nichrome is $1.30\times {10}^{-8}nm.$ Calculate the length of this wire that would be needed to make an element of an electric heater of resistance $30\Omega .$

This is a circuit

When switch $\mathrm{S}$ is open the current in ammeter $\mathrm{A}$ is $0.48$ A. Calculate the e.m.f. of the battery. You may assume the battery has negligible internal resistance.

This is a circuit

When switch $\mathrm{S}$ is closed the current in the ammeter increases to $0.72 \mathrm{A}$.

Determine the current in the $6.4\Omega$ resistor if current in ammeter A is $0.48A$.

This is a circuit

When switch $\mathrm{S}$ is closed the current in the ammeter increases to $0.72 \mathrm{A}$.

State the current in the thermistor.

This is a circuit

State and explain how the reading on the ammeter changes when the temperature of the thermistor is increased.