Question 3

An electric iron of resistance 20 Ω takes a current of 5 A. Calculate the heat developed in 30 s.

Answer

The amount of heat (H) produced is given by the joule’s law of heating as

H = VIt

Where,

Current, I = 5 A

Time, t = 30 s

Voltage, V = Current × Resistance = 5 × 20 = 100 V

H = 100 x 5 x 30 = 1.5x10⁴ J

Therefore, the amount of heat developed in the electric iron is 1.5x10⁴ J.

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