Monday, January 26, 2026

Important definitions:

One ampere: One ampere is the current constituted by the flow of one coulomb of charge per second.
One volt: One volt is the potential difference between two points in a current carrying conductor when 1 joule of work is done to move a charge of 1 coulomb from one point to the other.
One ohm: If the potential difference across the two ends of a conductor is 1 V and the current through it is 1 A, then the resistance R, of the conductor is 1 Ω.
One watt: One watt is the power consumed by a device that carries 1 A of current when operated at a potential difference of 1 V.
One unit of electric energy: One unit of electric energy is the energy consumed when 1 kilowatt of power is used for 1 hour.

Important information/formulae

Sr. No.	Description	Formula	More information
1	Relationship between current and charge	𝑰=	Where, I – current Q – charge t – time
2	Relationship between potential difference, work done and charge	𝑽=	Where, V – potential difference W – work done Q – charge
3	Ohm’s law	V = IR	Where, V – potential difference I – current R – Resistance
4	Resistance	𝑹 =	Where, R – resistance of a wire l – length of the wire A – cross-section area of the wire ρ – resistivity of the conducting material of the wire
5	Electric power	P = VI Or P = I²R Or P =	Where, P – electric power V – potential difference I – current R – resistance of the conductor
6	Joule’s law of heating	H = I²Rt	Where, H – heat energy I – current R – resistance t – time
7	System of 3 resistors connected in series	Rs = R1 + R2 + R3	Where, Rs - Effective resistance of the series combination of three resistors R1, R2 and R3
8	System of 3 resistors connected in parallel	= + +	Where, Rp – Effective resistance of the parallel combination of the three resistors R1, R2 and R3