  # Electricity Class 10 Science Chapter 12 Class 10 Science Chapter 12 in NCERT Science deals with Electricity. The chapter Electricity class 10 includes all the important concepts about Electric Current, Resistance and Various Elements of Electric Circuits and Relations between them. It also includes important practical topics like Heating Effect of Current, Electric Power and detailed insight of Commercial Unit of Electric Energy and how to calculate them are included in the chapter.

NTSE Guru helps you to boost your preparation with the most probable questions in accordance with the revised pattern of X board examination by our expert team of faculties.

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## Class 10 Science Chapter 12 - Important Questions

1. “Repulsion is the surest test of electrification” comment.

Ans.  Suppose we have to test a body (A) whether it is charged or not .Then, bring a charged body near A. If A is attracted then it is concluded that A may be charge body but we are not sure, because if A is uncharged than in vicinity of charged body, opposite charge gets induced in it & it gets attracted towards charged body.

On the other hand if, the body to be tested (A) is repelled then we are sure that it must possess like charge as that on the charge body.

This proves that repulsion is the surest test of electrification.

2. a) Explain why a comb rub through one’s hair attracts small bits of paper. What happens if the hairs are wet or if it is a rainy day?

(b)  Ordinary rubber is an insulator, but the special rubber tyres of air craft’s are made slightly conducting. Why is this necessary?

(c) Vehicles carrying inflammable materials usually have metallic ropes touching the ground during motion. Why?

(d) A bird perches on a base high power line & nothing happens to the bird. A man standing on the ground touches the same line gets a fatal shock. Why?

Ans. (a) It is because charge developed on comb due to friction. If the hairs are wet or if it is a rainy day then friction between the hair & comb is reduced, due to which charge cannot be developed on comb and it fails to attract small bits of paper.

(b) It is because due to friction between tyres and runway, the charges generated may go to earth, due to which any unwanted hazard can be checked.

(c)  Due to friction of air, body of the vehicle may gets charged. Similarly due to friction between tyres and road, charge can also be developed on tyres. The metallic rope transfer the accumulated charge to the earth, otherwise it may be dangerous with inflammable substances.

(d) For the flow of electric current, potential difference is required. As both the feet of the bird are at the same potential, so current cannot flow through bird. So bird remains quite safe. While in case of man there is a potential difference between power line and ground, so current will flow and he may get fatal shock.

3.  A2 Coulomb charge is carried from a point A which is at 20 Volt to another points B. If the work done in the process is 100 Joule, calculate the potential of point B.

Ans. Let potential at point at A = $${{V}_{A}}$$

Potential at Point B = $${{V}_{B}}$$

Then,

Potential Difference = $$\frac{\text{work}\,\,\text{done }\left( W \right)}{\text{charge}\,\left( Q \right)}$$

$${{V}_{B}}-{{V}_{A}}=\frac{W}{Q}$$

$${{V}_{B}}-20=\frac{100}{2}$$

$${{V}_{B}}=50+20$$

$${{V}_{B}}=70$$ Volt

4. What do you mean by the term ‘Electric current’? Also define one Ampere.

Ans. The rate of flow of electric charge through any cross section of a conductor is called electric current.

Its S.I. unit is Ampere.

Electric current flowing through a conductor is said to be 1 Ampere if, one Coulomb of electric charge flows through any cross section of the conductor in 1 second.

5. State Ohm’s law.

Ans. Ohm’s law : –   According to this law, current flowing through a conductor is directly proportional to the potential difference applied across the ends of the conductor, provided the physical conditions like temperature, Pressure etc. remain constant.

If V is the potential difference applied,

I is the current flowing

Then according to Ohm’s law

$$I \propto V$$

or   $$V \propto I$$

or   V = RI

Here, R is a constant of Proportionality which is known as electrical resistance of the conductor.

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