An electric heater of resistance 8 ? draws 15 A from the service mains 2hrs.Calculate the rate at which heat is developed in the heater.

Asked by saif abbas | 11th Sep, 2010, 04:59: PM

Expert Answer:

Heat generated per unit time (i.e., power, as in Watts, Joules per second) is given by 
P = VI =RI2      where V is the voltage across the wire (Volts), 
			       R is the wire resistance (Ohms), and 
                               I is the current (Ampere).
Therefore, amount of heat generated in time t
= RI2t 
= 8 x (15x15) x (2x60x60)                                             [assuming resistance is 8 ohms. u didnt give the unit]
= 12960 kJ

Answered by  | 11th Sep, 2010, 07:01: PM

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