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Calculating the 'heat dissipation' (power output as heat) in a component of a circuit

First of all you have to calculate the voltage across each component.

See circuit analysis

Once we have the value of each resistance and the p.d. across each one it is easy to work out the current passing through a component. We just use V =I R.

To calculate the heat dissipated in a component

Whenever a current passes through a component electrical energy is changed into heat energy.

The dissipation of energy as heat is calculated using

P = IV

where

    • P is power (energy in unit time – W - watts (J/s - joules per second).
    • I is the current in amps
    • V is the potential difference across the component

But you do not need to work out the voltage and current - you can calculate power from other combinations:

Using V = I R we can substitute into this equation:

P = IV

As V = I R

so, P = I(IR) = I 2 R

Or as I = V/R

so, P = (V/R) V = V 2/R

So, P = IV = I2 R = V 2/R

 

 

 

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