In class

1. What does LED stand for?

Ans: Light Emitting Diode

2. What are the benefits of using LEDs?

Ans: The benefits of using LEDs are:

         a. It consumes less energy.

         b. It lasts longer.

         c. It does not produce enormous heat like the electric bulb.

         d. It is almost unbreakable.

In class

1. Why are switches made of plastic?

Ans: The switches are made of plastics. Since plastic is an insulator so it protects the user from electric shocks.

2. Does a mobile phone need electricity to work?

Ans: Yes, mobile phone needs electricity to work.

EXERCISE

I. Tick (✓) the correct option to complete each sentence.

1. A set of electric cell is called

A switch/ a battery/ terminals/ a circuit

Ans: battery

2. The filament in a light bulb is made of

Tungsten / copper / aluminium / iron

Ans: tungsten.

3. The rod inside an electric cell is made of

Sodium / iron / carbon / copper

Ans: carbon

4. The material used to make the path of an electric circuit is

Iron / plastic / rubber / copper

Ans: copper

5. A device to complete an electric circuit is

An electrical switch / a battery / a cable / a cell

Ans: an electric switch.

II. Tick(✓) the true statements and cross(X) the false ones.

1. A bulb converts electrical energy to light energy. ✓

2. Plastic is a conductor of electricity. X

3. All electrical appliances have two terminals. ✓

4. Electric wires are covered with good insulators. ✓

5. Metals are good insulators. X

6. Bulbs last longer than LEDs. X

III. Answer the following questions in one sentence.

1. Why is tungsten used as a filament in a bulb?

Ans: Tungsten is used as a filament in a bulb because tungsten does not get melt down easily.

2. Which gas is filled in an electric bulb?

Ans: Argon gas is filled in an electric bulb.

3. Why are switches used in an electric circuit?

Ans: Switches are used in an electric circuit for completing or breaking an electric circuit.

4. Electric wires are made of copper. Why?

Ans: Electric wires are made of copper because copper is a good conductor and is much cheaper.

5. Why are electric wires covered with plastic?

Ans: Since plastic is is an insulator. It makes sure that if anybody touches the wire, he or she will not get electric shocks. 

IV. Answer the following questions in two sentences.

1. What are good conductors of electricity? Give one example.

Ans: The materials that allow electricity to pass through them are called good conductors of electricity. Example: copper.

2. What produces electricity in an electric cell?

Ans: The chemicals present inside an electric cell reacts to produce electricity.

3. Why are electric bulbs filled with argon gas?

Ans: Electric bulbs are filled with argon gas which protects the filament from heat and prevents it from breaking.

4. Why are LEDs preferred than ordinary bulbs?

Ans: LEDs are preferred than ordinary bulbs because it is user friendly, it uses less electricity and  lasts long as well as almost unbreakable.

5. What is an electric circuit?

Ans: The flow of electricity through a conductor is the electric current.

V. Answer in about four to five sentences.

1. How do LEDs work?

Ans:  A LED has two terminals namely positive and negative terminals. When the positive terminals is connected to the positive terminal and negative terminal is connected to the negative terminal of the battery then the electricity will pass through the LED and it starts to glow.

2. What is the importance of a switch in an electric circuit?

Ans: The switch is an important part of an electric circuit.It allows users to turn on electric appliances in need and keep the appliances off when there is no need. By completing the circuit it allows the electricity to flow through the circuit and by breaking it prevents electricity to flow through the circuit.

3. Explain the working of an electric switch.

Ans: When the switch is in the 'ON' position, it completes the circuit and the electric appliances works. But when the switch is in the 'OFF' position, the circuit is incomplete. Hence the electricity will not flow through the circuit and the electric appliances will not work.

4. Write a short note on 'Cell - a mini power plant'.

Ans: Cell is a mini power plant because it can produce electricity. It has some chemicals inside which reacts to produce chemical energy, which is then converted to electricity. When this chemicals get used up, the cell stops producing electricity and the appliances connected to it stops working.