ELECTRICITY , Class X, Part-1

                                                                                    ACCORDING TO THE CBSE SYLLABUS 2025-26, THIS CHAPTER HAS BEEN RENUMBERED AS CHAPTER 11.


CBSE CLASS 10 SCIENCE CHAPTER 12 ELECTRICITY NOTES -(PART I)


NOTES OF CHAPTER 12 ELECTRICITY, CLASS 10TH SCIENCE


Study Material and Notes of Ch 12 Electricity Class 10th Science

TOPICS IN THE CHAPTER

1. INTRODUCTION

2. CURRENT

3. POTENTIAL DIFFERENCE
 A. VOLT DEFINITION
 B. VOLTMETER

4. SYMBOLS OF SOME COMMONLY USED COMPONENTS IN CIRCUIT

5. Ohm's LAW
 A. MATHEMATICAL EXPRESSION FOR OHM'S LAW
 B. V-I GRAPH FOR OHM'S LAW
 C. RESISTANCE
 D. OHM
 E. RHEOSTAT

6. FACTORS ON WHICH THE RESISTANCE OF A CONDUCTOR DEPENDS
 A. RESISTIVITY

7. RESISTORS IN SERIES
 A. TOTAL/RESULTANT/OVERALL/EFFECTIVE RESISTANCE IN SERIES
 B. VOLTAGE ACROSS EACH RESISTOR

8. RESISTORS IN PARALLEL

9. ADVANTAGE OF PARALLEL COMBINATION OVER SERIES COMBINATION

10. HEATING EFFECT OF ELECTRIC CIRCUIT
 A. JOULE'S LAW HEATING EFFECT OF ELECTRIC CURRENT
 B. The filament OF AN ELECTRIC BULB IS MADE UP OF TUNGSTEN
 C. ELECTRIC FUSE
 D. ELECTRIC POWER
 
INTRODUCTION

The Class 10 science chapter 12, ‘Electricity’, attempts to answer questions like what constitutes electricity, what are some of the factors that control or regulate the flow of electricity, and how electricity flows in an electric circuit. The heating effects of electric current and its applications are also discussed in detail. In our attempts to understand the constitution of electric current, the atomic structure is discussed.
Electricity is an important source of energy in modern times. Electricity is used in our homes, in industry, and in transport. For example, electricity is used in our homes for lighting, operating fans, and heating purposes. In industry, electricity is used to run various types of machines, and in the transport sector, electricity is used to pull electric trains. To understand electricity, we must first understand electric charges. The flow of electric charges is called “electricity”. Electric charge has two types, positive and negative.
 
The charge is a fundamental particle in an atom. It may be positive or negative.
 a. Like charges repel each other.
b. Unlike charges attract each other.
c. Coulomb (C): S. I. unit of charge
d. 1 Coulomb charge = Charge present on approx. 6 × 1018 electrons
e. Charge on 1 electron = Negative charge of 1.6 × 10-19 C
n = No. of electrons
e = Charge on 1 electron
i.e. Q = ne
 
Where Q = Charge (total)

TYPES OF ELECTRIC CHARGES

Electric charges are of two types: positive and negative charges. The charge acquired by a glass rod when rubbed with a silk cloth is called a positive charge. The charge acquired by an ebonite rod when rubbed with a woollen cloth is called a negative charge.

IMPORTANT PROPERTY OFELECTRIC CHARGES

Opposite charges or unlike charges attract each other; for example, a positive charge attracts. Similar charges or like charges repel each other. This is also the fundamental law of electricity. For example, a positive repeal a positive charge and a negative charge repel a negative charge.

THE S.1 UNIT OF ELECTRIC CHARGE IS COULOMB

Which is denoted by the letter C. One coulomb is that quantity of electric charge which exerts a force of 9 x109 newtons on an equal charge placed at a distance of 1 meter from it.                   
Matter contains positively charged particles called protons and negatively charged particles called electrons. A proton possesses a positive charge of 1.6 x 10-19C. Whereas an electron possesses a negative charge of  1.6 x 10-19 C.
It is obvious that the unit of electric charge coulomb, is much bigger than the charge of a proton or an electron.

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.

ELECTRIC CURRENT

When two charged bodies at different electric potentials are connected by a metal wire, then electric charge will flow from the body at higher potential to the one at lower potential till they both acquire the same potential. This flow of charge in the metal wire constitutes an electric current. We now know that the electric charges that flow in a wire (metal wire) constitute electric current are negative charges (electrons).
The electric current is a flow of electric charges or electrons in a conductor (metal wire ). The magnitude of electric current in a conductor is the amount of electric charges passing through a given point of the conductor in one second.
If a charge of Q coulomb flows through a conductor in time t seconds, then the magnitude of the electric current I is flowing through it.
 
Current = Charge / Time
I = Q / T
 
1 A = 1 Cs-1
 1 mA = 10-3 A
 1 µA = 10-6 A
 
The S.I. unit of electric current is ampere (A).
When 1 coulomb of charge flows through any cross-section of a conductor in 1 second, the electric current flowing through it is said to be 1 ampere.
1 Ampere = 1 Coulomb / 1 second
1 A = 1C / 1 s
1 mA = 10-3 A ( mA = milliampere )
Current is measured by an instrument called an ammeter.

AMPERE (A)

The SI unit of current is ampere (A).

HOW  TO GET A CONTINUOUS FLOW OF ELECTRIC CURRENT?

The simplest way to maintain a potential difference between the two ends of a conductor so as to get a continuous flow of current is to connect the conductor between the terminals of a cell or a battery.

 DIRECTION OF ELECTRIC CURRENT

There are two types of electric current: negative and positive charge.
1. In the outer circuit, the current flows from the positive toward the negative terminal of the cell. This is known as conventional current.
2. In the inner circuit of the cell, current flows from the negative to the positive terminal of the cell.

The Current (I) is directly proportional to the potential difference applied across the ends of a conductor.

                                                                       I  ᾲ V

If the potential difference across the ends of a conductor is doubled, the current flowing through it also doubles.

                                                                        V  ᾲ I

If the potential is doubled = 2V

Then,                                                             2V ᾲ 2I

RESULT – The current flowing through it is also doubled.

If the potential difference is crossed, the ends of a conductor are halved, and the current is also halved.

                                                             V  ᾲ I

If the potential difference is halved = 1 / 2 V

Then,                                            1 / 2 V ᾲ 1/ 2 I

RESULT = Then the current flowing through it is also halved.

IMPORTANT CASES OF CURRENT AND RESISTANCE

 The current is inversely proportional to resistance.
                                                           I  ᾲ 1 / R
1. If the resistance is halved, the current is doubled.
                                                          R  ᾲ 1 / I
If the resistance is halved, = ½ R
Then ,                                             ½ R ᾲ 1 / 2 I

RESULT: The current flowing through it doubled.

 2. If the resistance is doubled, the current doubles.
                                                          R  ᾲ 1 / I
If the resistance is doubled = 2 R
Then ,                                                2 R ᾲ 2 /  I

RESULT: The current flowing through it was halved.

ELECTRIC POTENTIAL AND POTENTIAL DIFFERENCE (V)

The electric potential at a point is defined as the 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. The electrons move only if there is a difference in electric pressure called the potential difference. One Volt is defined as the energy consumption of one joule per electric charge of one coulomb.

V = W/Q

where V is the potential difference, W is the work done, and Q is the electric charge.

Work done to move a unit charge from one point to another.

1 VOLT: 

When 1 joule of work is done in carrying one Coulomb charge, then the potential difference is called 1 volt.

S. I. unit of Potential difference = Volt (V)

1 V = 1 W / 1 Q = 1 JC - 1

 VOLTMETER:

 It is an instrument to measure the potential difference.
a. It has high resistance and is always connected in parallel. Symbol is
b. A cell is the simplest device to maintain a potential difference.
c. Current always flows from higher potential to lower potential.                   

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