Question

A nichrome wire used as a heater coil the resistance of 1 ohm/metre. For a heater of 1000 W at 200 V, the length of wire required will be
1. 5 m
2. 20 m
3. 40 m
4. 50 m

Answer 1

Correct Answer - Option 3 : 40 m

Concept:

When power and voltage rating of resistance is given then the total resistance of that wire can be calculated by

\(R = \dfrac{{V_{rated}^2}}{{{P_{rated}}}}\)

Calculation:

Given resistance per meter = 1 Ω/m

Vrated = 200 V

Prated = 1 kW = 1000 watt

\(R = \frac{{{{200}^2}}}{{1000}} = 40\;{\rm{\Omega }}\)

Length of the wire \(= \frac{{40}}{1} = 40\;{\rm{meter }}\)