Electrical 82513

How long will it take for a current of 8A in a resistance of 30 ohms to develop thermal energy of 3 MJ if the efficiency of converting electrical energy into heat is 90%?

Correct answer:

t =  28.9 min

Step-by-step explanation:

I=8 A R=30 Ω Q=3 1000 1000=3000000 J η=90%=10090=109=0.9  Q = η P t  P=R I2=30 82=1920 W t1=Q/(η P)=3000000/(0.9 1920)=9156251736.1111 s  t=t1 min=t1:60  min=1736.1111:60  min=28.9 min=28.9 min



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