1. To find the current flowing through a circuit, cover I in fig 4 with your finger, this leaves V over R to give the formula V/R.
2. To find the current I divide the voltage V, by the resistance R, to get the answer in amps.
3. To find resistance cover the R with your finger leaving the V above I or V/I,
4. Divide the Voltage V, by the Current I, to give the resistance in Ohms.
5. Finally to find Voltage cover the V with your finger to show IR,
6. Multiply the resistance R, by the current I, to get the answer in Volts.

A practical illustration of the use of Ohms Law is given in the circuit on the right

When Sw1 is closed, the 12 volt battery forces electrons from the negative (-ve) terminal along the conductor and through the lamp Lp1 causing it to light, the current carries on through Sw1 and back into the battery via the positive (+ve) terminal.

If the lamp in Fig 5 has a resistance of 24 Ohms.

• Find the current flow through the circuit by the use of the Ohms Law formula.

When you have completed your calculation use a digital multimeter set to read the Amps reading as a check on the accuracy of your calculation.

• You will find the figures do not quite match even though you perform the calculation properly.
• This is due to the tolerances allowed in manufacturing of components.

Fig 5