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NCERT Class 10 Science Textbook Chapter 12 With Answer PDF Free Download
Chapter 12: Electricity
Electricity has an important place in modern society. It is a controllable and convenient form of energy for a variety of uses in homes, schools, hospitals, industries, and so on.
What constitutes electricity? How does it flow in an electric circuit? What are the factors that control or regulate the current through an electric circuit?
In this Chapter, we shall attempt to answer such questions. We shall also discuss the heating effect of electric current and its applications.
12.1 Electric Current And Circuit
We are familiar with air current and water current. We know that flowing water constitutes water current in rivers.
Similarly, if the electric charge flows through a conductor (for example, through a metallic wire), we say that there is an electric current in the conductor.
In a torch, we know that the cells (or a battery, when placed in proper order) provide a flow of charges or an electric current through the torch bulb to glow.
We have also seen that the torch gives light only when its switch is on. What does a switch do? A switch makes a conducting link between the cell and the bulb.
A continuous and closed path of an electric current is called an electric circuit. Now, if the circuit is broken anywhere (or the switch of the torch is turned off), the current stops flowing and the bulb does not glow.
How do we express electric current? Electric current is expressed by the amount of charge flowing through a particular area in unit time. In other words, it is the rate of flow of electric charges.
In circuits using metallic wires, electrons constitute the flow of charges. However, electrons were not known at the time when the phenomenon of electricity was first observed.
So, electric current was considered to be the flow of positive charges and the direction of flow of positive charges was taken to be the direction of electric current.
Conventionally, in an electric circuit, the direction of electric current is taken as opposite to the direction of the flow of electrons, which are negative charges.
12.2 ELECTRIC POTENTIAL AND POTENTIAL DIFFERENCE
What makes the electric charge flow? Let us consider the analogy of the flow of water. Charges do not flow in a copper wire by themselves, just as water in a perfectly horizontal tube does not flow.
If one end of the tube is connected to a tank of water kept at a higher level, such that there is a
the pressure difference between the two ends of the tube, water flows out of the other end of the tube.
For the flow of charges in a conducting metallic wire, the gravity, of course, has no role to play; the electrons move only if there is a difference in electric pressure – called the potential difference –
along the conductor.
This difference in potential may be produced by a battery, consisting of one or more electric cells.
The chemical action within a cell generates the potential difference across the terminals of the cell,
even when no current is drawn from it.
When the cell is connected to a conducting circuit element, the potential difference sets the charges in motion in the conductor and produces an electric current.
In order to maintain the current in a given electric circuit, the cell has to expend the chemical energy stored in it.
12.3 Circuit Diagram
We know that an electric circuit, as shown in Fig. 12.1, comprises a cell (or a battery), a plug key, electrical component(s), and connecting wires.
It is often convenient to draw a schematic diagram, in which different components of the circuit are represented by the symbols conveniently used. Conventional symbols used to represent some of the most commonly used electrical components are given in Table 12.1
12.4 OHM’S LAW
Is there a relationship between the potential difference across a conductor and the current through it? Let us explore with an Activity.
In this Activity, you will find that approximately the same value for V/I is obtained in each case. Thus the V–I graph is a straight line that passes through the origin of the graph, as shown in Fig. 12.3.
Thus, V/I is a constant ratio. In 1827, a German physicist Georg Simon Ohm (1787–1854) found out the relationship between the current I, flowing in a metallic wire, and the potential difference across its terminals.
The potential difference, V, across the ends of a given metallic wire in an electric circuit is directly proportional to the current flowing through it, provided the temperature remains the same.
|No. of Pages||24|
|PDF Size||3.6 MB|
NCERT Solutions Class 10 Science Chapter 12 Electricity
1. Name a device that helps to maintain a potential difference across a conductor.
A battery consisting of one or more electric cells is one of the devices that help to maintain a potential difference across a conductor.
2. What is meant by saying that the potential difference between two points is 1 V?
When 1 J of work is done to move a charge of 1 C from one point to another, it is said that the potential difference between two points is 1 V.
3. How much energy is given to each coulomb of charge passing through a 6 V battery?
We know that the potential difference between two points is given by the equation,
V = W/Q, where,
W is the work done in moving the charge from one point to another
Q is the charge
From the above equation, we can find the energy given to each coulomb as follows:
W = V × Q
Substituting the values in the equation, we get
W = 6V × 1C = 6 J
Hence, 6 J of energy is given to each coulomb of charge passing through a 6 V of battery.
In text 12.5 Page: 209
1. On what factors does the resistance of a conductor depend?
The resistance of the conductor depends on the following factors:
a. Temperature of the conductor
b. The cross-sectional area of the conductor
c. Length of the conductor
d. Nature of the material of the conductor
2. Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
Resistance is given by the equation,
R = ρ l/A
ρ is the resistivity of the material of the wire,
l is the length of the wire
A is the area of the cross-section of the wire.
From the equation, it is evident that the area of the cross-section of the wire is inversely proportional to the resistance. Therefore, the thinner the wire, the more the resistance and vice versa. Hence, current flows more easily through a thick wire than a thin wire.
Electricity NCERT Textbook With Solutions PDF Free Download