Exercise 2.32 A household uses 22 kWh day^-1 of electricity Part A How many kJ d
ID: 884629 • Letter: E
Question
Exercise 2.32 A household uses 22 kWh day^-1 of electricity Part A How many kJ day^-1 are used? Express your answer using two significant figures. Part B About 1 kW m^-2 of energy from the Sun hits the surface of Earth. With a 10% efficient solar battery, what area (in m2) of solar battery would be needed to provide enough solar energy to supply the household? Assume an average of 5 h day^-1 of sunshine. (A suitable energy-storage device would of course be needed to provide electricity at night.) Express your answer using one significant figure.Explanation / Answer
A)
we need to convert 22 kWh to KJ
22 kWh = 22 kW * 3600 s
= 79200 KWs
= 79200 KJ
because J = watt * second
so,
22 kWh day-1 = 79200 KJ day-1
Answer: 7.9*10^4
B)
Energy required per day = 79200 KJ
Let area be A m^2
Power available for harnessing from sun= 10 % of 1*A
=0.1 A KW
Sun is out for 5 hour = 3600*5 s = 18000 S
Energy available for harnessing from sun in 1 day = 0.1A * 18000 = 1800 A KJ
1800 A = 79200
A = 44 m^2
Answer: 44 m^2
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