Ohm's Law

Before exploring Ohm’s laws, we must revisit the following concepts. However, these topics will be covered in, Current and flow of electrons.

1. Electric current (I):  It is the measure of how much charges (or electrons) pass across any cross-section of a conductor in a certain given time. 

Therefore;

Electric current (I) =(Charge (Q))/(Time (t))

Or;

I =Q/t

It is measured in Amperes (A).

2. Potential difference or voltage (V): It is the difference between the concentrations of electrons (potential) across the two ends of the conductor. This difference help charges to move in the circuit.

It is measured in volts (V).

3. Resistance (R): It is the obstruction offered by the conductor to the flow of current in it.

It is measured in Ohms (Ω).

Ohm’s law explains the behaviour of the flow of electric current through a conductor concerning the potential difference maintained across the terminals of the electric circuit. An electrical circuit is formed when a conductive path is created to allow the electric charge to continuously flow.

German scientist Georg Simon Ohm found out that the voltage and current in a circuit depend directly upon each other provided the circuit remained under same physical conditions.

Ohm’s law states that he current flowing through any cross-section of the conductor is directly proportional to the potential difference applied across its ends provided physical condition like temperature and pressure remain constant.

That is; using the proportionality sign, we have;

Voltage (V)∝Current (I)

Or;

V∝I

This means as voltage increases current will also increase and vice-versa. In other words, voltage and current have a direct relationship. 

Removing the proportionality sign, we have;

V=IR

Here ‘R’, which is the resistance of the conductor, is the constant of proportionality. 

Mr Ohm found out that the relationship between voltage and current is such that, the increase in voltage is equal to the product of the current flowing through the conductor and the resistance offered by it. 

The relation between voltage, current, and resistance is the consequence of Ohm’s law.

From Ohm’s law, we can define resistance as the ratio of the potential difference applied across its terminals to the electric current flowing through the conductor.

That is;

R=V/I

Example 1:

What is the voltage of an electric fan if it draws a current of 2A through a resistance of 50Ω.

Solution:

Given:

I=2A

R=50Ω

We know;

V=IR

We have;

V=2×50=100V

Therefore, the voltage is 100V.

Example 2:

An electric water boiler draws a current of 5A when a voltage of 230V is applied to it. Find the resistance of the water boiler.

Solution:

Given:

I=5A

V=230A

We know;

R=V/I

That is;

R=230/5=46

Therefore, the resistance of a wire is 46Ω