Question

An electric immersion heater of $1.08 \,kW$ is immersed in water. After the water has reached a temperature of $100^{\circ }\,C,$ how much time will be required to produce $100\, g$ of steam?

• A. 50s
• B. 420s
• C. 105s
• D. 210s

Answer 1

Answer: (D)

210s

Answer 2

$L$ is the latent heat of vaporization of water; the heat required for producing $1 \,g$ of steam,
$L=540\, cal =540 \times 4.2=2268\, J$
Energy supplied
$=1080\, J / s$
Time required to boil $100 \,g$ of water
$=540 \times 4.2 \times 100 / 1080$
$=210\, s$