Name the conductor which have almost no resistance?

Superconductors.
For example: Mercury at 4.2 K

Class X TBSE some intext and parallel questions and their answer.

Chapters are acid, base and salt; chemical reaction

TBSE class X Safety measure for electrical circuit

What are the differences between AC and DC?

Alternating Current	Direct Current
a.       It is safe to transfer over longer city distances and will provide more power.	a.       Practically the voltage of DC cannot travel very far until it begins to lose energy.
b.      The frequency of alternating current will not be zero e.g. 50Hz in our country.	b.      The frequency of direct current will always be zero.
c.       It reverses its direction while flowing in a circuit.	c.       It only flows in one direction in the circuit.
d.      It is the current of magnitude which is varying with time	d.      It is the current of constant magnitude.
e.      It is more dangerous than DC	e.      It is less dangerous than AC

What are the precautions are to be taken in using electricity?

Precautions to be taken while working with electricity:

1. We should avoid water at all times when working with electricity. Never touch or try repairing any electrical equipment or circuits with wet hands.

2. Equipment with frayed cords, damaged insulation or broken plugs should never be used.

3. If we are working on any receptacle at our home then always turn off the mains. It is also a good idea to put up a sign on the service panel so that nobody turns the main switch ON by accident.

4. We always need to use insulated tools while working.

5. Electrical hazards include exposed energized parts and unguarded electrical equipment which may become energized unexpectedly. Such equipment always carries warning signs like “Shock Risk”. 

6. We need to always use appropriate insulated rubber gloves and goggles while working on any branch circuit or any other electrical circuit.

7. Also we should know the wire code of your country.