**CBSE Class 10 Science Chapter 12 Electricity Notes: **Download PDF Here

## Atomic Structure

- An atom has a positively charged nucleus and negatively charged electrons revolving around it.
- Valence electrons in metals are free to move within the conductor and constitute an electric current.

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Charge

The charge is an intrinsic property of matter by virtue of which it can exert electromagnetic force.

## Conductors and Insulators

A substance which offers comparatively less opposition to the flow of current is known as conductors and substances which offer larger opposition are insulators.

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### Electric Potential and Potential Difference

The electric potential at a point is defined as work done in bringing a unit positive charge from infinity to that point. The potential difference between two points is defined as the difference in electric potentials at the two given points.

## Models of Electric Current

### Electric Current(I)

Flow of electric charges is called electric current, i.e, I = Q / t

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### Electron sea model

Electric current in a solid conductor is due to drift of a ‘sea’ of free electrons, which are free to jump onto any neighbouring atom.

### Drift velocity of Electron

Average velocity which an electron attains inside a metallic conductor due to the application of an electric field due to the potential difference.

### Battery and its working

A cell is a source of potential difference, which is created inside it due to internal chemical reactions.

At anode: Cu(s)⇌Cu2+(aq)+2e−

At cathode: Ag(aq)+2e−⇌2Ag(s)

A combination of cells is called a battery.

## Electric Circuit

### Electric circuit and circuit diagram

- A closed-loop path which a current takes is called an electric circuit.
- Representation of an electric circuit through symbols is called a circuit diagram.

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## Resistance and Ohm’s Law

### Ohm’s law

The current flowing through an ohmic conductor is directly proportional to the applied potential difference between the two ends of the conductor.

#### For More Information On Resistance and Ohm’s Law, Watch The Below Video:

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### Resistance

Resistance is a measure of the opposition offered to the current flow in an electric circuit.

### Factors affecting Resistance & How they affect

Resistance is:

- directly proportional to the length of the conductor.
- directly proportional to nature of the conductor.
- directly proportional to the temperature of the conductor.
- inversely proportional to the cross-sectional area of the conductor.

#### For More Information On Factors Affecting Resistance, Watch The Below Video:

### Resistivity

The electrical resistance offered by a substance of unit length and unit cross-sectional area is called resistivity.

### Ohmic and Non-Ohmic resistors

Resistors which follow Ohm’s Law are called Ohmic resistors and those which do not follow it are called Non-Ohmic resistors.

### Superconductors

Conductors which offer zero resistance to the flow of current are called superconductors.

## Combination of Resistors

### Combination of resistors

- Two resistors are said to be combined in series if they carry the same current.
- Two resistors are said to be combined in parallel if the same potential difference is applied to them.

### Equivalent Resistance of a system of resistors

The equivalent resistance of two resistors is given as:

- In series, Req=R1+R2
- In parallel, 1/Req= 1/R1+ 1/R2

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### EMF and Terminal Voltage

- EMF: The potential difference between the two terminals of a cell, when there is no current flowing through the circuit.
- Terminal voltage: The potential difference between the two terminals of a cell, when current is flowing through the circuit.

## Electric Power and AC

### Heating Effect of Current

Joule’s Law:

- Heat (H) ∝ square of the current (I).
- H ∝ Resistance of the given circuit.
- H ∝ Time (t) for which current flows through the conductor.

When a potential difference is established, it causes electrons to move, i.e. flow of current.

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### Electric Power

- The rate of doing work or rate of consumption of electrical energy is called Electric Power. If W is work done in time t, then P=W/t.
- S.I unit is Watt(W). One watt of power is consumed when 1 A of current flows at a potential difference of 1 V.
- The commercial unit of electrical energy is a kilowatt-hour (kWh).
- 1kWh = 3,600,000J = 3.6×106J
- Represented as P=I2R and P=V2/R
- One kilowatt-hour is defined as the amount of energy consumed when 1kW of power is used for 1 hour.

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