Why formula for heat generated in electric circuit is H= i^2Rt, While formula for heat dissipation in circuit is H= i^2R Shouldn't these be same as all the generated heat is dissipated eventually?
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$\begingroup$ Energy is power multiplied by time. $\endgroup$– John DotyCommented Nov 5, 2022 at 12:37
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$\begingroup$ @JohnDoty but heat dissipated is also form of energy just as the heat generated $\endgroup$– Gagan YadavCommented Nov 5, 2022 at 12:41
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$\begingroup$ Heat dissipated, expressed as power, is the rate at which heat is dissipated. It is not the total amount of heat dissipated. $\endgroup$– John DotyCommented Nov 5, 2022 at 12:44
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$\begingroup$ Are km/hr and km the same thing? $\endgroup$– John DotyCommented Nov 5, 2022 at 12:44
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$\begingroup$ Oh okk, thank you sir that cleared the misconception I had😊👍 $\endgroup$– Gagan YadavCommented Nov 5, 2022 at 12:46
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2 Answers
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The symbol $H$ has been used to mean two different things.
. . . . formula for heat dissipation in circuit is $H= i^2R$.
In this expression $H$ is power which is the rate of heat dissipation per second.
. . . . heat generated in electric circuit is $H= i^2Rt$.
In this expression $H$ is the heat (energy) dissipated in a time $t$ seconds.
The linking equation is, $\text{ energy in joules = power in watts }\times \text{time in seconds}$.
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Yes, eventually the system will come to steady state with all the heat generated being dissipated. But the design issue for this electronics cooling system is: How high in temperature does the electronics get when this steady state is attained? This depends on the turbulent heat transfer coefficient between the electronic and the cooling air, the amount of area over which the heat transfer takes place, and the mass flow rate of the air.
answered Nov 6, 2022 at 12:29