The resistance of each of the three wires joined as shown in figure is `4 Omega` and each one can have a maximum power of 20 watt (otherwise it will melt). What maximum power will the whole circuit dissipate ?

Explanation

Let `I` be the current through a resistance wire of maximum power 20 watt.
`:. I^(2)R = 20 or I^(2) xx 4 = 20 or I^(2) = 5`
Effective resistance `R_(p)` between A and C will be `R_(p) = ( 4 xx 4)/(4 +4 ) = 2 Omega`
Electric power dissipated as heat by the resistance between A and C `= I^(2)R_(p) = 5 xx 2 = 10` watt.
Electric power dissipated as heat by the resistance between C and B `= I^(2)R = 5 xx 4 = 20` watt.
`:.` Total electric power dissipated as heat by the whole circuit `= 10 +20 = 30` watt.