Question

Three resistors A,B,C are connected as shown in the figure.Each of them dissipates energy to maximum of 18 W .Find the maximum current that can flow through three resistors.

Answer 1

V= voltage across a resistor
I = current through the resistor
R = value of resistance.

Power  dissipated by the resistor is given by : P =  V²/R = I² R
       I² = P / R

Each resistance dissipates energy = 18 Watts

Maximum current through B or C or A is given by : I² = 18 Watts/2 ohms
           So I = 3 Amperes maximum

Since the resistances B and C are connected in parallel, the current that comes from the resistance A is divided equally between the resistance B and C.
   so current through  B = current through resistance C = 1/2 * current thru A

Since, the current passing thru resistor A is max = 3 ampere, then the current through resistor B and resistor C  are 1.5 Amperes maximum.

Answer 2

I=√P/√R

I= √18/2

I=3A

So,max current=3A