Topic Menu

Cyber-chess a chess instruction site

Resistivity Question

Q3.

(a) For a conductor in the form of a wire of uniform cross-sectional area, give an equation which relates its resistance to the resistivity of the material of the conductor. Define the symbols used in the equation.

(2 marks)

(b) An electrical heating element, made from uniform nichrome wire, is required to dissipate 500 W when connected to the 230 V mains supply.

(i) The cross-sectional area of the wire is 8.0 × 10–8 m2. Calculate the length of nichrome wire required. resistivity of nichrome = 1.1 × 10–6 Ω m

(ii) Two heating elements, each rated at 230 V, 500 W are connected to the 230 mains supply (A) in series, (B) in parallel.

Explain why only one of the circuits will provide an output of 1 kW.

(6 marks)

(Total 8 marks)