The voltage on the bulb is 120 V and the resistance is 400 ohms. Find the amperage.

Given:

U = 120 Volts – light bulb voltage;

R = 400 Ohm is the resistance of the light bulb filament.

It is required to determine I (Ampere) – the strength of the electric current passing through the filament of the light bulb.

To determine the magnitude of the current, it is necessary to apply the following formula (Ohm’s law for a section of the circuit):

U = I * R, from here we get that:

I = U / R = 120/400 = 12/40 = 3/10 = 0.3 Amperes.

Answer: the strength of the electric current is 0.3 amperes.