Electricity Class 10th Notes - Free NCERT Class 10 Science Chapter 12 Notes - Download PDF

Ever wondered how electric bulbs glow or why wires heat up when current flows through them? These kinds of questions you will learn in Class 10 Science Chapter 11: Electricity. This chapter helps you to understand how electric current flows, how circuits work and how to calculate electrical energy. NCERT Notes class 10 science chapter 11 electricity topics are important for board exams and science olympiads like NSO, NSEJS etc.

These Notes are created by a Careers360 subject matter expert as per the latest CBSE syllabus. These NCERT notes cover important concepts like electric current, potential difference, Ohm’s Law, resistance, resistors in series and parallel, and the heating effect of electric current. These NCERT notes also include key formulas, diagrams, and real-life examples to make understanding and revision easy for every student.

Also Read,

• NCERT Solutions for Class 10 Science Chapter 11 Electricity
• NCERT Exemplar Class 10 Science Chapter 11 Electricity

NCERT Class 10 Science Chapter 11 Notes

Electric Current and Circuit

Electric Current

The rate of flow of electric charges through any cross-section of a conductor is called electric current. If a net charge $Q$ passes through a cross-section in time $t$, then electric current $l$ is

$
I=\frac{Q}{t}=\frac{\text { charge }}{\text { time }}
$

(i) The current is a fundamental quantity in physics with unit ampere (A). So 1 A is the amount of current flowing in the circuit if 1 C of charge moves across it in 1 s .
(ii) The conventional direction of current is taken to be the direction of flow of positive charge or opposite to the direction of flow of electrons.
(iii) A conductor remains uncharged when current flows through it.
(iv) For a given conductor, the current flowing through it does not vary as its cross-sectional area varies.

Electric Potential and Potential Difference

Electric potential may be defined as the amount of work done in bringing a unit positive charge from infinity to a point under consideration, while the electric potential difference between two points in an electric circuit may be defined as the amount of work done to move a unit positive charge from one point to another. Thus, when a charge $Q$ is moved from point $A$ to point $B$ in an electric circuit, and $W_{A B}$ work is done, then potential difference between them is

$V_B-V_A=\frac{W_{A B}}{Q}$

The SI unit of electric potential difference is volt (V), named after Alessandro Volta (1745-1827), an Italian physicist. 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.

$
\text { Therefore, } 1 \text { volt }=\frac{1 \text { joule }}{1 \text { coulomb }}
$

Circuit Diagram

• A conducting path between the terminals of a source of electricity and other electronic devices in continuity is called an electric circuit.

• A schematic diagram showing the way different electronic devices are connected in a circuit is known as a circuit diagram.

The various conventional electrical symbols used to represent some of the most commonly used electrical components in an electrical circuit diagrams are as follows :

Ohm’s Law

• The current (I) flowing through a conductor is directly proportional to the potential (V) across its ends at a constant temperature.

  $
  \begin{aligned}
  & V \propto I \\
  & V=R I
  \end{aligned}
  $

  where, $R$ is the constant of proportionality and is called the resistance of the conductor. It is the property of a conductor to resist the flow of charges through it.

• The property of conductors to resist the flow of current is known as Resistance.

• S.I. unit of resistance = ohm (Ω).

• R=V/I gives us 1 Ohm=1Vol/1Ampere

Factors on Which the Resistance of a Conductor Depends

The resistance of a conductor of uniform thickness depends on the length of the conductor ( $L$ ) and the area of cross-section ( $A$ ).

$
\begin{aligned}
& R \propto \text { length of conductor } \\
& R \propto \frac{1}{\text { Area of cross-section of the conductor }} \\
& R \propto \frac{L}{A} \quad \text { or } R=\rho \frac{L}{A} \quad \text { ( } \rho \text { is pronounced as rho) }
\end{aligned}
$

where $\rho$ (constant of proportionality) is called the specific resistance or resistivity of the conductor. It depends on the nature of the material of the substance, not on its shape and size. It is defined as the resistance offered by a wire of the material of unit length and unit cross-sectional area or we can also define resistivity as the resistance of a unit meter cube of that material.
The SI unit of resistivity is ohm-metre ( $\Omega-\mathrm{m}$ ). Reciprocal of resistivity is termed as conductivity. The conductivity or the specific conductance measures material's ability to conduct electric current.

$
\text { Conductance }=\frac{1}{\text { Resistance }}
$

It is represented by G and its unit is mho.

Resistance of a System of Resistors:

When multiple resistors are connected in a circuit, their total or equivalent resistance depends on how they are arranged:

1. Resistors in Series:

Total Resistance: $R_{\text {total }}=R_1+R_2+R_3+\ldots$

• Current remains the same through all resistors.
• Voltage divides across each resistor.

2. Resistors in Parallel:

Total Resistance: $\frac{1}{R_{\text {total }}}=\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}+\ldots$

• Voltage remains the same across all resistors.
• Current divides across each resistor.

Comparison or advantage of parallel combination over series combination

(i) In parallel combination we can operate each devices with its individual switch which is not possible in series combination.
(ii) All equipments work at same voltage.
(iii) As different equipments have different current ratings so they need different current and this possible only in parallel combination

Heating Effect of Electric Current

We have seen that when the electric current passes through a resistor, it becomes hot because the electric energy spent or electric work done in moving the charges is converted into heat energy.
Joule gave the law on heating effect of current known as Joule's law, which states that the heat produced in a resistor is directly proportional to the
(i) Square of the electric current for a given resistance, i.e., $H \propto R^2$.
(ii) Resistance for a given current, i.e., $H \propto R$.
(iii) Time for which the current flows through the resistor, i.e., $H \propto t$.

So, by this law, we get

$
H=I^2 R t
$

So, $H=I^2 R t=\frac{V^2}{R} \cdot t=V I t$

Practical Applications of the Heating Effects of Electric Current

• Electrical appliances like iron, oven, and heater are a few devices that are based on Joule’s Law of Heating.
• This phenomenon is also applied to produce light in a bulb.
• One of the most important applications of Joule’s Law of Heating is the fuse used in electric circuits.

Electric Power

Electrical power is the electrical work done per unit time or the rate at which electric energy is dissipated or consumed in an electric circuit.

$
\begin{aligned}
P & =\frac{\text { Work done }}{\text { Time taken }} \\
P & =\frac{W}{t}
\end{aligned}
$

• S.I. unit of power = Watt (W).

• 1 Watt of power is consumed when 1 A of current flows at a potential difference of 1 V.

• The commercial unit of electric energy is in kilowatt-hour (kWh), which is generally known as a Unit.

• 1kWh=3.6MJ

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