Question

Tell me everything about 12(Electricity) chapter of class 10th.

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Answer 1

Explanation:

Charge

Protons and electrons possess some charge. Proton has positive charge. Electron has negative charge. Neutron does not possess any charge. Like charges repel each other and unlike charges attract each other.

Conductors and Insulators

Conductors are those materials in which electrons can move freely. All metals are conductors. Insulators do not have any free electrons to move. For example, wood and plastic.

Electric Current

The flow of electric charge is known as Electric Current. It is expressed in terms of rate of flow of charges.

Formula of Electric Current

The SI unit of electric current is Ampere (A).

Direction of electric current is same as direction of positive charges and opposite to the direction of flow of negative charges.

Potential Difference

Work done per unit charge in taking charge from one point to another is known as Potential Difference. The unit of potential difference is volt (V). 1V is defined as the potential difference between two points if 1 Joule of work is done to move 1 coulomb charge from one point to another.

Ohm’s law

Potential difference between two points is directly proportional to the current, provided temperature is constant.

V ∝ l

⇒ V = lR

R is a constant known as Resistance. The SI unit of resistance is ohm (Ω)

Factors on which resistance of a conductor depends-

It is directly proportional to length of conductor.

Inversely proportional to the area of cross-section.

Directly proportional to the temperature.

Depends on nature of material.

Resistivity

Resistivity is the property of the material. The SI unit of resistivity is ohm-metre.

Resistivity of metals varies from 10-8 to 10-6.

Resistivity of insulators varies from 1012 to 1017

Copper and aluminium are used in electrical transmission due to their low resistivity.

Resistance = Resistivity * Length of Conductor/Cross Sectional Area

Resistors in series

When two or more resistors are joined in series, then their total resistance is given by the formula-

Resistors in Series

RS = R1 + R2 + R3

The current will remain same through all resistor. Total voltage is given by-

V = V1 + V2 + V3

Voltage across each resistor is given as –

V1 = lR1

V2 = lR2 [V1 + V2 + V3 = V]

V3 = lR3V = lR

⇒ V = lR1 + lR2 + lR3

lR = l(R1+ R2 + R3)

R = R1 + R2 + R3

Resistors in parallel

In this case, voltage is same across each resistor and is equal to applied voltage. Total current is given as-

Resistors in parallel

V/R = V/R1 + V/R2 + V/R3

1/Rp = 1/R1 + 1/R2 + 1/R3

Advantages of Parallel Combination over Series Combination

If one component fails in series combination, then complete circuit is broken and no component can work properly. Different appliances need different current, this can be met through parallel.

Heating effects of Electric Current

When charge Q moves against the potential difference V in time t, the amount of work is given by-

Heating effects of Electric Current

Joule’s Law of Heating

Heat produced in a resistor is directly proportional to square root of current.

It is also directly proportional to resistance for a given current.

Also, directly proportional to time

H = l2 Rt

Filament of electric bulb is made up of tungsten because it has a very high melting point and also does not oxidize readily at a high temperature.

Electric fuse is a safety device to protect the electrical appliance from short circuit.

Electric Power

The rate at which electric energy is dissipated or consumed in an electric current. The SI unit of power is Watt.

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Answer 2

$\huge{\underline{\underline{\red{\tt{Electricity :}}}}}$

In this summary I will be providing every complete information about the Chapter - 12 Electricity

Let's begin

♣ Electricity : The Flow of electrons in an circuit it called Electricity.

♣ Electric Circuit : A continuous and closed path of an electric current is called electric circuit.

★ In an electric circuit Direction of current is taken opposite of the Direction of Electrons.

• Unit of Current (I) = Ampere (A)
• Unit of Charge (Q) = Coloumb(C)

We have any equation for charge and current relationship.

$\large{\boxed{\sf{I \: = \: \dfrac{Q}{t}}}}$

Where,

Current is denoted by I

Charge is denoted by Q

time is denoted by t

By the above equation we can come to know definition of 1 Ampere current

♣ 1 Ampere current is defined as When 1 Coloumb of charge is flowing in circuit in 1 second is called 1 Ampere.

♣ Ampere is also defined as rate of flow of charge.

♣ Current is measured through a devise called Ammeter.

♣ electrons in 1 Coloumb = 1.6*10^(18)

♣ Charge of electron = 1.6*10^(-19) C

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Potential Difference

Now let us read about Potential Difference

♣ Potential Difference is flow of charge in a metallic solid where electrons moves only under electric pressure is called potential Difference.

• Denoted by V
• Unit of Potential Difference is V (volt)

Formula for Potential Difference is :

$\large{\boxed{\sf{V \: = \: \dfrac{W}{Q}}}}$

Where W is work done

So,

♣ 1 Volt is defined as when 1 Joule of work is required to move 1 Coloumb of charge is called potential difference

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Circuit Diagrams

For the representation of the parts of a circuit we had to make certain circuit diagrams.

See attached picture (Fig. 1)

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Ohm's Law

We will find ohm's law by this method :

$\sf{V \: \propto \: I}$

V/I = constant

V/I = R

V = IR

So here the constant is R (Resistance)

• Symbol (R)
• Unit ohm Ω

Formula is R = V/I

♣ One ohm resistance is defined as when 1 volt of charge is moving 1 Ampere of current

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Some more concepts :

R ∝ L

R ∝ 1/A

R ∝ L/A

R = ρL/A

Where,

L is length

A is Area

and the constant ρ is rho.Unit Ωm

♣ Also there are two type of resistance :

1. Series
2. Parallel

In parallel we have formula

1/Rp = 1/R1 + 1/R2 + .............. + 1/Rn

And for Series is

Rs = R1 + R2 + ........ Rn

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Also some of the Formulas are :

• H = VIt
• P = VI
• H = I²Rt

Where,

H is heat energy

P is power

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