simulate this circuit – Schematic created using CircuitLab
The circuit above has total power dissipation of 60 watts. I need to calculate:
– Resistance of R2
Since it is given that total power is 60 watts, and the series circuit
has 120v, then we can calculate total resistance to be RT =
(120*120)/60 = 240 ohmsWe know we currently have a total known resistance of R1 + R3 = 180
ohms. So R2 = 240 – 180 = 60 Ohms
– Current in the circuit
If we calculated resistance of R2 correctly, then we know RT =
R1+R2+R3 = 240 ohmsWe know voltage gain VT = 120 Volts.
So total current: IT = VT/RT = 120/240 = 0.5 Amps
– Voltage across each resistor
Voltage across R1 = V1 = (0.5 A) * (80 ohms) = 40 Volts
Voltage across R2 = V1 = (0.5 A) * (60 ohms) = 30 Volts
Voltage across R3 = V1 = (0.5 A) * (100 ohms) = 50 Volts
To check if our answer is correct we total the voltages 40+30+50 =
120 Volts which is our total voltage.
Are my answers correct?
Best Answer
Your answers look correct.
As a cross check, you are given the voltage (120V) and the total power (60W). From that you can calculate the current directly.
P=EI, so 60W=120V*I.
I therefore has to be .5A, which matches your other results.