Paper 3 Current Electricity Fundamentals Drills

Q1 I-V characteristic and power

A component has the following data.

$V/\mathrm{V}$	0.0	1.0	2.0	3.0	4.0
$I/\mathrm{A}$	0.00	0.20	0.38	0.52	0.62

1. Explain whether the component is ohmic. [3]
2. Calculate resistance at $V=2.0\mathrm{V}$. [2]
3. Calculate power at $V=4.0\mathrm{V}$. [2]
4. Explain why resistance may increase with temperature in a metal filament. [3]

Q2 Drift speed

A copper wire carries current $1.20\mathrm{A}$. Its cross-sectional area is $3.0\times 10^{-7}{\mathrm{m}}^2$. The mobile electron density is $8.5\times 10^{28}{\mathrm{m}}^{-3}$.

1. Calculate the drift speed. [3]
2. Explain why drift speed is small although the circuit responds quickly. [3]
3. State the direction of electron drift relative to conventional current. [1]