Correct Answer: Option B

Explanation

Electrical heat generated = quantity of heat required to change water from liquid to vapour

I\(^2\) R t = mL

I = current = 10A, R = resistance = 2Ω, t = time = 20s, m = mass of water = 5 X 10\(^{-3}\)kg and L = specific latent heat of vaporization.

10\(^2\) x 2 x 20 = 5 X 10\(^{-3}\)L

4000 =  5 X 10\(^{-3}\)L

L = \(\frac{4000}{5\times10^{-3}}\) = 800000 ⇔ 8.0 x 10\(^5\)Jkg\(^{-1}\)

There is an explanation video available below.

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