Q1. Choose the correct option.
A Which of the following is a good conductor?
i. Metallic nail
ii. Eraser
iii. Wooden stick
iv. Plastic pen
Answer: i. Metallic nail
b. In a bulb, electricity is converted into:
i light energy
ii. sound energy
iii. chemical energy
iv. solar energy
Answer: Light energy
c. Which of the following statement/s is/are correct about current? Statement
I: Current is the flow of electric charges.
Statement II: Current can flow through an open circuit.
i. Only statement I
iii. Both statement I and II
ii. Only statement II
iv. Neither statement I nor II
Answer: i. Only Statement I
d. The device which is used to open or close an electric circuit is called a:
i. cell
ii. battery
Assertion-Reasoning questions
iii. switch
iv. connecting wire
Answer: iii. Switch
Q2. Assertion -Reasoning questions
For questions number (i) and (ii), two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
- Both assertion(A) and Reason (R) are true and Reason (R) is the correct explanation of the assertation (A)
- Both assertion (A) and reason are true and Reason (R) is not the correct explanation of the assertation (A)
- Assertion (A) is true but reason (R) is false
- Assertion (A) is false, but reason (R) is true.
- Assertion(A): The filament of an electric bulb is made up of tungsten.
Reason (R): Tungsten is a cheap metal and is easily available.
Answer: (c) – Assertion (A) is true, but Reason (R) is false.
Explanation: Tungsten is used because it has a high melting point, not because it’s cheap.
(ii) Assertion (A): Electrical wires are made up of metal.
Reason (R): Metals are good conductors of electricity.\
Answer: (a) – Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
Explanation: Metals are used in wires because they allow electricity to pass through easily.
Q3. Answer the following questions in one sentence.
a. What is the charge on an electron?
Answer: The charge on an electron is negative.
b. Name a device that converts mechanical energy into electrical energy.
Answer: A generator converts mechanical energy into electrical energy.
c. Name the unit which is used to measure electric current.
Answer: The unit used to measure electric current is the ampere.
d. Define electric circuit.
Answer: An electric circuit is a path through which electric current flows.
Q4. Answer the following questions in 2-3 sentences.
a. What is a battery? Draw the electric symbol of a battery.
Answer: A battery is a device made up of multiple cells that stores and provides electrical energy. Its symbol is two lines of different lengths; the longer one represents the positive terminal, and the shorter one represents the negative terminal.
b. What is an insulator? Give two examples of insulators.
Answer: An insulator is a material that does not allow electric current to pass through it. Examples of insulators are rubber and plastic.
c. What is an electric generator?
Answer: An electric generator is a machine that changes mechanical energy into electrical energy, often used in power stations.
d. What is importance of a switch in an electric circuit?
Answer: A switch allows us to control the flow of current in a circuit by opening or closing it, making it essential for safely operating electric devices.
Q5. Answer the following in 3-4 sentences.
a. How does an electric bulb work?
Answer: An electric bulb has a thin wire called a filament inside it. When electric current flows through the filament, it heats up and starts to glow, producing light. The filament is often made of tungsten because it can withstand high temperatures.
b. Explain the types of electric cells. Give one example of each type of cell.
Answer: There are two main types of electric cells: primary cells and secondary cells. Primary cells, like alkaline batteries, cannot be recharged. Secondary cells, like lithium-ion batteries, can be recharged and used multiple times.
c. Explain with the help of a diagram, how current flows from a cell to the bulb.
Answer: In a simple circuit, current flows from the positive terminal of the cell through a wire to the bulb, lighting it up, and then flows back to the negative terminal of the cell, completing the circuit.
d. List any four precautions that must be taken while handling electricity.
Answer:
- Do not touch electrical devices with wet hands.
- Avoid using damaged wires or cords.
- Keep electrical appliances away from water.
- Turn off the main switch during repairs.