Physics 9702 · AS & A Level · Force on a moving charge

Force on a moving charge — practice question

A magnetic field with flux density $B$ is perpendicular to face $PQRS$ of a slice made of conducting material, as Fig. 9.1 shows. A current $I$ in the slice is perpendicular to face $QRZY$ of the slice. The Hall voltage $V_H$ across the slice is given by $V_H = \dfrac{BI}{ntq}$.
(a(i))[1]

State what the symbol $n$ stands for.

(a(ii))[1]

The symbol $t$ is the length of one side of the slice. Use the letters in Fig. 9.1 to identify $t$.

(b(i))[2]

Usually, the Hall voltage from a slice of metal is very small. For a slice with the same dimensions carrying the same current and in the same magnetic flux density, the Hall voltage from a semiconductor is much larger. Suggest and explain why.

(b(ii))[3]

In some semiconducting materials, electrons are mainly responsible for conduction. In other semiconducting materials, holes are mainly responsible for conduction. Suggest and explain what difference, if any, conduction by electrons or by holes will make to the Hall voltage.

(ii)[3]

In some semiconducting materials, electrons are the main charge carriers. In other semiconducting materials, holes are the main charge carriers. Suggest and explain whether conduction by electrons or by holes has any effect on the Hall voltage.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: Charge-carrier number density / free-electron number density

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