Two 100 Ohm and 200 Ohm light bulbs are connected in series to a 120 V network.

Two 100 Ohm and 200 Ohm light bulbs are connected in series to a 120 V network. Determine the amperage in the circuit and in each lamp.

U = 120 V.

R1 = 100 ohms.

R2 = 200 ohms.

I -?

I1 -?

I2 -?

When the conductors are connected in series, the current in the circuit I and the current in each conductor are the same: I = I1 = I2.

The total resistance of series-connected resistances, R, is the sum of the resistances of each conductor: R = R1 + R2.

R = 100 ohms + 200 ohms = 300 ohms.

According to Ohm’s law for a section of a circuit, the current in the circuit I is directly proportional to the voltage U and inversely proportional to the resistance of the circuit R: I = U / R.

I = 120 V / 300 Ohm = 0.4 A.

Answer: the current in the circuit and each lamp is I = I1 = I2 = 0.4 A.