Question 22
Quantity of HeatAn electric kettle with negligible heat capacity is rated at 2000 W. If 2.0 kg of water is put in it, how long will it take the temperature of water to rise from 20 °C to 100 °C? [Specific heat capacity of water = 4200 J kg−1 K−1]
- A.420 s
- B.336 s
- C.168 s
- D.84 s
Show the answer and explanation
Answer: B (336 s)
Explanation
Heat needed = mcΔθ = 2 × 4200 × 80 = 672 000 J. Time = 672 000 ÷ 2000 = 336 s.