Introduction to Electricity NCERT Lessons For Class 10th
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What is Electricity?
- If you look around yourself you will see almost everything is run by Electricity.
- It is a convenient and important source of energy
- It is used in homes,industries,transport and many more.
What is Charge
Understanding Charge
- Bring a plastic comb near some very tiny pieces of paper, there will not have any effect on them.
- When you rub the comb with dry hair and then taken near the tiny pieces of paper, we find that the comb now attracts the pieces of paper towards itself.
- These observations are explained by saying that initially the comb is electrically neutral so it has no effect on the tiny pieces of paper.
- When the comb is rubbed with dry hair, then it gets electric charge.
- This electrically charged comb exerts an electric force on the tiny pieces of paper and attracts them
What is Electric Charge
- Electric charge is a basic property of electrons, protons and other subatomic particles.
- Electrons are negatively charged while protons are positively charged.
- Like charges repel each other and unlike charges attract each other.
- SI unit of Electric Charge is coulomb(C).
- An Electron posses a negative charge of 1.6×10-19C
What is Electric Current
- when electric charge comes in motion then electric current forms.
- Or rate of change of electric charge is called as electric current.
- If a net charge Q flows across any cross-section of a conductor in time t then the current current I, through the cross section is
We know that the charge of an electron is 1.6 × 10–19 coulomb (or 1.6 × 10–19 C).
Now, If charge is 1.6 × 10–19 C, No. of electrons = 1
If charge is 1 C, then No. of electrons=
We are given, I = 0.5 A; t = 10 min = 600 s.
we have
Q = It
= 0.5 A × 600 s = 300 C
Direction of flow of Electric Current
- When electricity was invented a long time back, it was known that there are two types of charges : positive charges and negative charges
- but the electron had not been discovered at that time.
- So, electric current was considered to be a flow of positive charges and the direction of flow of the positive charges was taken to be the direction of electric current
- The actual flow of electrons (which constitute the current) is, however, from negative terminal to positive terminal of a cell, which is opposite to the direction of conventional current
Lets go to a new part i.e. Electric Potential so,
What is Electric Potential
- The Electric Potential or Potential at point in an Electric Field is defined as the work done in moving an unit positive charge from infinity to that point.
- Potential is denoted by the symbol V and its unit is Volt.
- Potential of 1 Volt at a point means 1 joule of work is done in moving 1 coulomb of positive charge from infinity to that point.
Now we will now discuss the more common term i.e. the Electric Potential Difference
so, What is Potential Difference
- The Potential Difference between two points in an electric circuit is defined as the amount of work done in moving an unit charge from one point to other point.
- Potential difference (V) between two points = Work done (W)/Charge (Q)
- V = W/Q
1 volt = 1 joule /1 coulomb
1 V = 1 J C–1
Thus, the amount of work W, done in moving the charge is
W = VQ
= 12 V × 2 C= 24 J.
We know that :
Potential difference =Work done/ Charge moved
or V =W/Q
Here, Potential difference, V = 128 – 118 = 10 volts
Work done, W = ? (To be calculated)
And, Charge moved, Q = 2 coulombs
Putting these values in the above formula, we get : 10 =W/2 or W = 10 × 2
Thus, Work done, W = 20 joules
