The thin wire in an electric bulb that produces light is called the filament. Due to high resistance of the filament and heating effect of electric current, filament glows and gives us light.

Definition: 1 Mark
Answer: 1 Mark
An arrangement that provides a complete path for electricity to pass (current to flow) is known as an electric circuit.
No, electric current will not flow in an open circuit.

Number of terminals 1 Mark
Reason: 1 Mark
An electric cell has two terminals; positive and negative. The metal cap is the positive terminal and metal disc is the negative terminal.
An electric cell has two terminals because the two terminals can be connected via some load to form an electric circuit (which provides a closed path for current to flow). A circuit should always be closed for current to flow through it.

If we directly connect the two terminals of a cell without connecting them to a switch or a bulb then the chemicals in the electric cell will get used up very fast. Eventually, the cell will get discharged and stop working.

Solution: 1 Mark
Explanation: 2 Marks
Coversion into conductor: 2 Marks
Distilled water is the purest form of water and it acts as an insulator.
For conduction of electricity, water should have dissolved ions in it but distilled water does not have any ions for conduction of electricity.
To conduct electricity through distilled water, we need to add some impurities such as salts. Tap water and sea water contain some traces of salts and impurities, due to which they become good conductors of electricity.

Definition: 1 Mark 
Classification: 2 MarkS
Conductors are materials which allow electricity to pass through them.
Insulators are materials which do not allow current to pass through it.
Conductors:  Copper, silver, iron, steel, tap water, sea water

Components: 2 Marks
Wires: 1 Mark
In general, a circuit has the following components:

1) A cell or battery: source of electricity

2) Connecting wires: conductor

3) Key or switch

4) Bulb or electric device
Metal wires are used in electric circuits because the metals are good conductors of electricity and allow current to pass through them.

Materials: 2 Marks
Reason: 3 Marks
Electricians should wear gloves made of rubber, plastic. These materials are non-conductors of electricity so they would not allow electricity to pass through them.
Electricians work on electric devices or circuits which may contain live wires (wires carrying current) and they may accidentally come in contact with them. The human body is also a good conductor so electricians may get shock.
Rubber is a good insulator. To prevent themselves from electric shock or flow of current, the electricians use rubber gloves while repairing.

Purpose: 2 Marks
Gadgets: 1 Mark
An electric switch is a device which is used to break or complete an electric circuit. 
Switches are widely used in different electrical or electronic gadgets. Examples: toggle switches used in houses, pushbutton switches used in microwaves, water pump, mobile phones,TV.