# Ncert 12th Physics Chapter-3

## Potentiometer

Chapter-3|Current Electricity| NCERT 12th Physics: Potentiometer: A long wire (of few metres) of uniform cross section area.   Applications: 1. To measure EMF of a cell: We will find null point on wire where G shows no deflection.   2. To compare of EMF of two cells:   3. To measure internal resistance of a …

## Meter Bridge

Chapter-3|Current Electricity| NCERT 12th Physics: Meter Bridge: It is a electrical instrument. It measured the value of unknown resistance. It works on the principle of wheatstone bridge.   Wire of length 1 m=100 cm and uniform cross section area A. Wire must be so that it is temperature independence (does not increase resistance after increasing …

## Wheat Stone Bridge

Chapter-3|Current Electricity| NCERT 12th Physics: Wheat Stone Bridge: In balanced wheat stone Bridge, If there is no current in mid register(R₅) and X and Y have same potential, then   Proof: Let there is no current in mid register. To Prove:-  R₁/R₂=R₃/R₄   Find the equivalent resistance between A and B.

## How to Apply Kirchhoff’s Law

Chapter-3|Current Electricity| NCERT 12th Physics: How to Apply Kirchhoff’s Law: 1.  Draw current from one or more cells (According to yourself). 2. Choosing a loop- (I) It should be closed loop. (II) It can involves any number of cells, registers, capacitance, etc. 3. Direction of loop or Path- You can take clockwise, anticlockwise or anyone …

## Kirchhoff’s Rule

Chapter-3|Current Electricity| NCERT 12th Physics: Kirchhoff’s Rule: Kirchhoff’s First Rule: The algebric sum of the currents meeting at a point in an electric circuit is always zero. Or The sum of current entering the junction is equal to the sum of current leaving the junction.   Kirchhoff’s Second Rule(Loop Rule, Voltage Law): “The algebraic sum …

## Combinations of Cells

Chapter-3|Current Electricity| NCERT 12th Physics: Combinations of Cells Two Cells in Series: When two cells are connected in series, then total EMF of cells Eeq= E₁+E₂ and total internal resistance req= r₁+r₂   If Cells Are Connected – to – And + to + Terminal in Series:   Two Cells in Parallel: When two cells …

## Relation Between Terminal Potential Difference, EMF of Cell and Internal Resistance of a Cell

Chapter-3|Current Electricity| NCERT 12th Physics: Relation Between Terminal Potential Difference, EMF of Cell and Internal Resistance of a Cell: Let a cell of EMF E and internal resistance r connected to an external resistance R. let a constant current I flows through this circuit.

## Cells and Electromotive Force(EMF) of a Cell

Chapter-3|Current Electricity| NCERT 12th Physics: Cells and Electromotive Force(EMF) of a Cell: Cells: An electric cell is a source of energy that maintains a continuous flow of charge in a circuit. Electric cell changes chemical energy into electrical energy. Electromotive Force(EMF) of a Cell: Electric cell has to do some work in maintaining the current …

## Electrical Power

Chapter-3|Current Electricity| NCERT 12th Physics: Electrical Power: It is defined as the rate of electrical energy supplied per unit time to maintain flow of electric current through a conductor.   One Watt: Power of an electric circuit is said to be 1 Watt, If 1 ampere current flow in it against a potential difference of …

## Electrical Energy

Chapter-3|Current Electricity| NCERT 12th Physics: Electrical Energy: It is defined as the total work done W by the source of emf V in maintaining the electric current I in the given circuit for a specified time t. According to Ohm’s law   V= IR Total charge that cross the register   q=It

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