Electricity: Ohm's Law

Numerical Problems

These numerical problems are based on the chapter Electricity class 10 science of NCERT book and CBSE syllabus.

Example 1: Calculate the resistance if 5 A of electric current flows through a conductor having potential difference between two points is equal to 15 V.

Solution: Given, electric current (I) = 5 A

Potential difference (V) = 15 V

Resistance (R) =?

We know from Ohm's Law that

`R=V/I`

Or, `R=(15V)/(5A)=3Ω`

Example 2: If the potential difference between the terminals of an electric motor is 220 V and an electric current of 5 A is flowing through it what will be the resistance of electric motor?

Solution: Given, electric current (I) = 5 A

Potential difference (V) = 220 V

Resistance (R) =?

We know from Ohm's Law that

`R=V/I`

Or, `R=(220V)/(5A)=44Ω`

Example 3: An electric current of 15 A is flowing through an electric fan. If the potential difference between two terminals of electric fan is 240 V, what will be resistance?

Solution: Given, electric current (I) = 15 A

Potential difference (V) = 240 V

Resistance (R) =?

We know from Ohm's Law that

`R=V/I`

Or, `R=(240V)/(15A)=16Ω`

Example 4: If the resistance of an electric iron is 48 Ω and an electric current of 5 A is flowing through it, what will be the potential difference between two terminals of electric iron.

Solution: Given, electric current (I) = 5 A

Resistance (R) = 48Ω

Potential difference (V) =?

We know from Ohm's Law that

`R=V/I`

Or, `V=RxxI`

Or, `V=48Ωxx5A=240V`

Example 5: Calculate the potential difference between two points of a terminal, if an electric current of 10 A is flowing through it having resistance of 20Ω.

Solution: Given, electric current (I) = 10 A

Resistance (R) = 20Ω

Potential difference (V) =?

We know from Ohm's Law that

`R=V/I`

Or, `V=RxxI`

Or, `V=20Ωxx10A=200V`

Example 6: If the resistance between two terminals of an electric heater is 15Ω and an electric current of 15 A is flowing through it then what will be the voltage of electric current?

Given, electric current (I) = 15 A

Resistance (R) = 15Ω

Voltage, i.e. Potential difference (V) =?

We know from Ohm's Law that

`R=V/I`

Or, `V=RxxI`

Or, `V=15Ωxx15A=225V`