14. Sources of Energy

1. What is a good source of energy?

Answer

We can say that a good source of energy would be one

 • which would do a large amount of work per unit volume or mass,

 

• be easily accessible,

 

• be easy to store and transport, and

 

• perhaps most importantly, be economical.

2. What is a good fuel?

Answer

It releases more heat on burning. It produce a little of smoke and is easily available?

3. If you could use any source of energy for heating your food, which one would you use and why?

Answer

I can use LPG gas because it doesn't produce smoke and easily available and it releases more heat on burning.

Electricity

Q.No.1. What does an electric circuit mean ?

Answer

An electric circuit means a continuous and closed path of an electric current.

Q.No. 2. Define the unit of current.

Answer

The electric current is expressed by a unit called ampere (A), named after the French scientist, Andre-Marie Ampere . One ampere is constituted by the flow of one coulomb of charge per second, that is, 1 A = 1 C/1 s.

Q.No. 3. Calculate the number of electrons constituting one coulomb of charge.

Answer

We know that

1.6×10-¹⁹ coulomb charge = 1 Electron.

or, 1 coulomb charge = 1÷(1.6×10-¹⁹) Electrons.

or, 1 coulomb charge = 6×10¹⁸ Electrons.

Q.No.1. Name a device that helps to maintain a potential difference across a conductor.

Answer 

Battery or a combination of cells helps to maintain a potential difference across a conductor. 

2. What is meant by saying that the potential difference between two points is 1 V?

Answer 

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.

Therefore,

1 volt = 1 joule/1 coulomb

1 volt = 1joule per coulomb. 

1 V = 1 J/C.

3. How much energy is given to each coulomb of charge passing through a 6 V battery?

Answer 

Work done = Potential difference×Charge 

or, Work done = 6×1

or, Work done = 6 joule.

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