Question

The circuit shown is used to control the brightness of two identical lamps. The variable resistor is adjusted until the lamps operate at their correct voltage of 3.0V

1) When the lamps operate at the correct voltage, the reading on the ammeter is 1.2A. Calculate the current in one lamp.

Answer 1

Since the lamps are identical, the current divides equally through them... 0.6A through each lamp.

Answer 2

You don't have to worry about voltage drop or the value of the resistor to make that 9 volt drop to happen. The current is divided evenly by the two lamps. If the ammeter reads 1.2 amps before the current goes into the lamps then since this is a parallel circuit, the lamps will divide up the current evenly between them.

That's another way of saying each one will get 1.2 amps /2 = 0.6 amps.