Hello and welcome to Just Answer. My name is ***** ***** I will be happy to assist you with your electrical question.
1) Since each light bulb is 12 volts and there are a total of 4 bulbs, the circuit source voltage = 12V x 4 = 48 volts.
2) Each bulb = 18 watts and each bulb has a voltage drop of 12 volts, solve for current (I). Apply Ohms Law where I = P/E. I = 18W/12V = 1.5 amps = total circuit current.
3) Next solve for Total Power by applying Watts Law where P = I x E. P = 1.5 amps x 48 volts = 72 total watts. Check by adding each of the four 18 watt light bulbs (18+18+18+18) = 72 total watts or total power.
4) Next, solve for the individual resistance on each light bulb by applying Ohms Law where R = E/I. Since each bulb is 12 volts and a series current of 1.5 amps in the circuit, R = 12/1.5 = 8 ohms each light bulb. Since a total of four light bulbs in the circuit, the total circuit resistance = 8 x 4 = 32 ohms.
Check if 32 ohms is correct by applying Ohms Law where I = E/R. Solve for total circuit voltage. E = I x R = 1.5 X 32 ohms = 48 volts. Therefore, the total circuit resistance = 32 ohms.
If you have any additional questions, just let me know and I’ll be glad to answer them for you.
Otherwise, don’t forget to rate me before you log Off.