Question

Three resistors R_A, R_B and R_C are connected in series and to a 120volt source. If R_B = 2R_A, R_C = 3R_A , when the circuit current is 10 amp, calculate the resistance of each resistor.  

Answer 1

$$R_{eq}=R_A+R_B+R_C=V/I=120/10=12\Omega.\\ R_{eq}=R_A+2R_A+3R_A=6R_A=12\Omega,\\ R_A=2\Omega.\\ R_B=2R_A=4\Omega,\\ R_C=3R_A=6\Omega.$$