Learn how to calculate resistance in series and parallel circuits.

Part of

- Question
- Calculate the total resistance of the circuit.
- Calculate the current flowing in the resistor.
- Calculate the voltage across the resistor.
- Calculate the current flowing in the resistor.

1. First calculate the parallel resistance:

R

_{1}=R

_{2}=R =

R =

This is in series with the . The total resistance R is given by:

R = R

_{1}+ R_{2}R =

R =

The total resistance of the circuit is .

2. The circuit above has now been simplified to:

Hence, the voltage across the resistor is 12 V.

I =

V = 12 V

R =

I =

I = 1.87 A

The current is the same in all parts of a series circuit and so this is the current through the resistor too.

The current flowing in the is 1.87 A.

3. The current through the resistor is not known so we cannot use V = IR to calculate the voltage across it directly.

However, we do know the current through the resistor, so we can calculate the voltage across it.

V = IR

I = 1.87 A

R =

V = 1.87 A x

V = 5.61 V

The total voltage = 12 V

Hence, the voltage across the two parallel resistors = 12 V – 5.61 V = 6.39 V.

The voltage across each parallel resistor is the same.

Hence, the voltage across the = 6.39 V.

The voltage across the 8Ω resistor is 6.39 V.

4. The voltage across each parallel resistor is the same.

Hence, the voltage across the resistor = 6.39 V.

I =

V = 6.39 V

R =

I =

I = 1.07 A

The current through the is 1.07 A.