Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage or potential difference between the two points provided the temperature is constant for a constant length and area.

Ohm’s Law Formula

Voltage = Current × Resistance

V = I × R

Where, V = voltage (Unit: volts or V), I = current (Unit: Amperes or A) and R = resistance (Unit: ohms or Ω)

Here, we have three resistors (labelled R1, R2, and R3) connected in a long chain from one terminal of the battery to the other.

• In a series circuit, there is only one path for the current to flow.

• In this circuit, the current flows in a clockwise direction, from point 1 to point 2 to point 3 to point 4 and back to 1.

The formula for resistance connected in series :

Series: R = R1 + R2 + R3

Lets calculate the resistance in this circuit:

Formula for resistors connected in series:

R = R₁ + R₂+ R₃

=3kΩ + 10kΩ + 5kΩ

= 18kΩ ( kilo ohms)

Again, we have three resistors, R1, R2, R3 connected in a long chain from one terminal of the battery to another.

• But this time they form multiple continuous paths for the current to flow.

  • One path from 1 to 2 to 7 to 8 and back to 1 again.

  • Another from 1 to 2 to 3 to 6 to 7 to 8 and back to 1 again.

  • And a third path from 1 to 2 to 3 to 4 to 5 to 6 to 7 to 8 and back to 1 again.

• In a parallel circuit, all components are connected between the same set of electrically common points.

  • In the diagram, points 1, 2, 3, and 4 are all electrically common.

  • Same for points 8, 7, 6, and 5.

  • Note: all resistors, as well as the battery, are connected between these two sets of points.

The formula for resistance connected in parallel :

Parallel: 1/R=1/R1+1/R2+1/R3

Let's calculate the resistance of this circuit:

Formula for resistance connected in parallel:

1/R = 1/R₁ + 1/R₂ +1/ R₃

=1/10kΩ + 1/2kΩ + 1/1kΩ

=16/10kΩ

=8/5kΩ

Then R = 5/8kΩ