**OHM’S LAW: **Ohm’s law states about the relation between voltage, current and resistance in a D.C circuit.

This law states that, *if the temperature of the conductor material is constant, the ratio of voltage and current between any two points on the conductor is constant, known as resistance.*

So, V/I= constant = R.

R is the resistance between the two points.

**OHM’S LAW TRIANGLE**: The triangle representation of ohm’s law is easy to remember the equation.

**ELECTRICAL POWER IN D.C CIRCUIT**: Electric power denoted as P is the product of voltage and current.

P= V X I Watt = I X R X I Watt = I^{2}R Watt.

or, P = V X V / R = V^{2}/R Watt.

The power triangle shown as

**ELECTRIC RESISTANCE**: This is the fundamental property of a substance due to which it resists the flow of current through it, or it is defined as the ratio of applied voltage(V) and flowing current (I) through it.

R = V / I.

The symbol of resistance is R.

When a potential difference applied across a conductor, free electrons moves and collide with other atoms and producing heat. The property due to which it opposes the conductivity of electron is called resistance.

● Those materials which offer greater opposition, known as poor conductor or **insulator**.

● On the other hand which offer less opposition known as **good conductor**, that means, relatively smaller external force is required to produce a flow of current.

Silver, Aluminium, Copper are good conductor whereas, paper, dry wood, glass, rubber are known as poor conductor or insulator.

So, we can say, ** Resistance is an element which convert electric energy into heat.**.

**UNIT OF RESISTANCE**: As per **George Simon Ohm**, the S.I unit of resistance is ohm and represented by Ω. According to ohm’s law, 1 ohm resistance is equal to the flow of 1 ampere current by the voltage of 1 volt.

1 kΩ = 1000 Ω.

1 MΩ = 10^{6}Ω.