Resistance, Resistivity & Potential Dividers (Edexcel International A Level Physics)

A filament lamp is marked 12 V 60 W. The filament is made from a long metal wire with a diameter of 0.25 mm. The metal has a resistivity of 5.6 × 10⁻⁸ Ω m when the wire is at normal operating temperature.

Calculate the length of the wire in the filament.

Length of wire = .........................................

A student has two filament lamps. Lamp A is marked 12 V 60 W and lamp B is marked 12 V 30 W. The student sets up the circuit shown.

The student states that both lamps will operate normally.

Evaluate whether the student’s statement is correct.

A nichrome wire of length 0.45 m has a cross-sectional area of 2.5 × 10^–7 m².

The resistance of the wire is 2.0 Ω.

Calculate the resistivity of nichrome.

Resistivity = ...................................

A potential difference of 3.0 V is applied across the nichrome wire.

Calculate the drift velocity of the conduction electrons in the nichrome wire.

number of conduction electrons per m³ = 9.0 × 10²⁸ m^–3

Drift velocity = .................................

A student suggests that the drift velocity will double if the length of wire used in the circuit is halved.

Comment on this suggestion.