If the filliament resistance in an automobile headlamp is 3 ohms, how many amps does it draw when connected to a 12 volt battery? I got 36 watts?
would I divide 12 volts/3 ohms= 4 amps
Correct
To calculate the amount of current drawn by the headlamp, you can use Ohm's Law, which states that the current (I) flowing through a conductor is equal to the voltage (V) divided by the resistance (R):
I = V / R
In this case, the voltage (V) is 12 volts and the resistance (R) is 3 ohms. Thus, the calculation would be:
I = 12 volts / 3 ohms
I = 4 amps
Therefore, the headlamp draws 4 amps of current when connected to a 12-volt battery. Your calculation of 4 amps is correct.