Mastering Ohm's Law with Practical Examples

Ohm's law is named after the scientist Dr. Ohm.

It states the relationship among voltage the voltage across resistor R is measured to be equal to V volts and the current through it is measured to be equal to I amperes.

Then the ohm’s law relates V, I and R. current and resistance.

Statement of Ohm’s law
The ohm’s law states that the ratio of potential difference (V) between any two points and the current flowing between them is constant if temperature is constant. This ratio is termed as resistance R.

ohm's law unit is Ω

Fig. Electric circuit to understand ohm's law

V/I = Constant = R ohms

R = V/I

Where

R = resistance of the conductor

V = Voltage across conductor

I = Current through the conductor

Ohm’s law means that the current I will increase or decrease in proportion with the increase or decrease of the voltage applied and the constant of proportionality is called as the resistance R.

V = I.R

Example

Ex.3.1. A resistance of 15 Ohm carries a current of 5Amp. Calculate the voltage developed across the resistor.

Soln.: V = IR=5x15=75Volts

Ex.3.2. If a potential difference of 50 V appears across a resistor of 5 Ohm, calculate the current flowing through the resistor.
Soln.:

I= V/R

50/5 =10Amp

Ex.3.3. Calculate the resistance of an iron filament if it operates on 230 V supply and draws a current equal to 2 amperes.
Soln.:
Note that the iron filament is a linear device. Hence the ohm’s law is applicable here even though it is an AC circuit.
Resistance of the iron filament = R = 230V/2 =115 Ohm

Ex.3.4. If a potential difference of 100 V appears across a resistor of 10 Ohm, calculate the current flowing through the resistor.
Soln.:

I= V/R

100/10 =10Amp

Ex.3.5. If a potential difference of 220 V appears across a resistor of 25 Ohm, calculate the current flowing through the resistor.
Soln.:

I= V/R

220/25 =8.8Amp

Ex.3.6. A resistance of 30 Ohm carries a current of 10Amp. Calculate the voltage developed across the resistor.

Soln.: V = IR=10x30=300Volts

Ex.3.7. If a potential difference of 40 V appears across a resistor of 5 Ohm, calculate the current flowing through the resistor.
Soln.:

I= V/R

40/5 =8Amp

Ex.3.8. If a potential difference of 240 V appears across a resistor of 5 Ohm, calculate the current flowing through the resistor.
Soln.:

I= V/R

240/5 =48Amp

Ex.3.9. If a potential difference of 10 V appears across a resistor of 2 Ohm, calculate the current flowing through the resistor.
Soln.:

I= V/R

10/2 =5Amp

Ex.3.10. If a potential difference of 8 V appears across a resistor of 2 Ohm, calculate the current flowing through the resistor.
Soln.:

I= V/R

8/2 =4Amp

Ex.3.11. If a potential difference of 75 V appears across a resistor of 10 Ohm, calculate the current flowing through the resistor.
Soln.:

I= V/R

75/10 =7.5Amp

Ex.3.12. If a potential difference of 65 V appears across a resistor of 4 Ohm, calculate the current flowing through the resistor.
Soln.:

I= V/R

65/4 =16.25Amp

Ex.3.13. If a potential difference of 90 V appears across a resistor of 10 Ohm, calculate the current flowing through the resistor.
Soln.:

I= V/R

90/10 =9Amp

Ex.3.5. If a potential difference of 140 V appears across a resistor of 5 Ohm, calculate the current flowing through the resistor.
Soln.:

I= V/R

140/5 =28Amp