An electric generator coupled to a windmill produces an average electric power output of 15 kW. The power is used to charge a storage battery. Heat transfer from the battery to the surroundings occurs at a constant rate of 1.8 kW. Determine, for 8 h of operation

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Explanation:

The electric power generated by the windmill = P = 15 kW.

Heat dissipation by the battery = Q = 1.8 kW.

The power is generated for 1 hour.

we know, 1 kW = 1 kJ/s

Hence,

P=15*60*60 = 54000 kJ

Q=1.8*60*60 = 6480 kJ

Net power stored in the battery,

Δ

E

=

P

-

Q

Δ

E

=

54000

-

6480

Δ

E

=

47520

k

J

Total amunt of energy stored in the battery is 47520 kJ.