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 = I2R Watt.
or, P = V X V / R = V2/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 = 106Ω.

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