Electricity Free Lesson for Class 10 Science NCERT

7 Topics | 2 Quizzes
Light – Reflection and Refraction

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**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.**

**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**

**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-**^{19}C

**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

**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**

**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.**

**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 isW = VQ= 12 V × 2 C= *

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**

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