IB Physics SL B.5.9 Current and charge flow Question Bank

Practise IB Physics SL B.5.9 by calculating current as charge flow and applying drift speed, carrier density and wire area.

Exam points

Use I=ΔQ/Δt to calculate charge flow through wires, liquids, batteries and electron beams.
Apply I=nqAv to determine drift speed or current when carrier density and cross-sectional area are given.

[Maximum number: 1]

In an experiment a student constructs the circuit shown in the diagram. The ammeter and the voltmeter are assumed to be ideal.

Figure for Question B.5.9—Current and charge flow question 1 — IB Physics SL

A connecting wire in the circuit has a radius of 1.2 mm and the current in it is 3.5 A . The number of electrons per unit volume of the wire is $2.4 \times 10^{28} \mathrm{~m}^{-3}$ . Show that the drift speed of the electrons in the wire is $2.0 \times 10^{-4} \mathrm{~ms}^{-1}$ .

$3.5=2.4 \times 10^{28} \times \pi\left(1.2 \times 10^{-3}\right)^{2} \times 1.6 \times 10^{-19} \times v\left\|\Rightarrow v=2.0 \times 10^{-4} \mathrm{~ms}^{-1}\right\| v$

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B.5.9—Current and charge flow question 1