How long does it take a 750 W heater operating at full rating to raise the temperature of 1 kg of water from 40oC to 70oC? (Take the specific heat capacity ...
Question 1 Report
How long does it take a 750 W heater operating at full rating to raise the temperature of 1 kg of water from 40oC to 70oC? (Take the specific heat capacity of water as 4200 J kg-1 K-1 and neglect heat losses).
Answer Details
To solve this problem, we can use the formula:
Q = mcΔT
Where Q is the heat energy required, m is the mass of water, c is the specific heat capacity of water, and ΔT is the change in temperature.
We can calculate Q as follows:
Q = (1 kg) x (4200 J/kg K) x (70°C - 40°C)
Q = 126,000 J
We can then use the formula:
P = Q/t
Where P is the power of the heater in watts and t is the time taken to heat the water.
Rearranging this formula to solve for t, we get:
t = Q/P
Substituting the values we know, we get:
t = (126,000 J) / (750 W)
t = 168 seconds
Therefore, it will take the 750 W heater operating at full rating 168 seconds to raise the temperature of 1 kg of water from 40°C to 70°C. The answer is (c) 168s.
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