Two 6 ohm and 18 ohm conductors are connected in series and included in a 120 volt circuit.

Two 6 ohm and 18 ohm conductors are connected in series and included in a 120 volt circuit. Find the voltage across each conductor.

R1 = 6 ohms.

R2 = 18 ohms.

U = 120 V.

U1 -?

U2 -?

We express the voltage across the resistances from Ohm’s law for a section of the circuit with the following formulas: U1 = I1 * R1 and U2 = I2 * R2.

When the conductors are connected in series, the current in the circuit and in each conductor is equal to each other: I = I1 = I2.

The total resistance R of the series-connected conductors with resistance R1 and R2 is the sum: R = R1 + R2.

Let’s write Ohm’s law for the whole chain: I = U / R = U / (R1 + R2).

I = 120 V / (6 ohms + 18 ohms) = 5 A.

U1 = 5 A * 6 Ohm = 30 V.

U2 = 5 A * 18 Ohm = 90 V.

Let’s check: U = U1 + U2.

U = 30V + 90V = 120V.

Answer: U1 = 30 V, U2 = 90 V.