Question 1: Fill in the blanks:
(a) A device that is used to break an electric circuit is called _______________.
(b) An electric cell has _______________ terminals.
Answer:
(a) A device that is used to break an electric circuit is called a switch. A switch is essential in controlling the flow of electric current in a circuit, allowing us to turn on or off electrical devices safely.
(b) An electric cell has two terminals, namely the positive and negative terminals. The positive terminal is usually marked with a plus (+) sign and is typically the metal cap of the cell, while the negative terminal is the metal disc on the opposite side.
Question 2: Mark ‘True’ or ‘False’ for the following statements:
(a) Electric current can flow through metals.
(b) Instead of metal wires, a jute string can be used to make a circuit.
(c) Electric current can pass through a sheet of thermocol.
Answer:
(a) True. Metals let electricity pass through them.
(b) False. Jute string can’t carry electricity like metal wires can.
(c) False. Thermocol doesn’t let electricity pass through; it’s an insulator.
Question 3: Explain why the bulb would not glow in the arrangement shown in Fig. 12.13.
Answer: The bulb doesn’t glow because the circuit is incomplete. There’s a gap or an insulator that stops electricity from reaching the bulb.
Question 4: Complete the drawing shown in Fig 12.14 to make the bulb glow.
Answer: Connect one wire to the bottom of the bulb and the other wire to the tip of the bulb’s base to complete the circuit and make the bulb glow.
Question 5: What is the purpose of an electric switch? Name some gadgets with switches.
Answer: An electric switch is used to turn electricity on or off for a device. Examples of gadgets with switches are lights, fans, and TVs.
Question 6: Would the bulb glow in Fig. 12.14’s circuit if we use an eraser instead of a safety pin?
Answer: No, the bulb won’t glow because an eraser is an insulator and doesn’t let electricity pass through it.
Question 7: Would the bulb glow in the circuit shown in Fig. 12.15?
Answer: No, the bulb won’t glow because the circuit is probably incomplete or broken.
Question 8: If a bulb glows using a “conduction tester” on an object, is the object a conductor or an insulator?
Answer: The object is a conductor because it lets electricity pass through it, making the bulb glow.
Question 9: Why should an electrician wear rubber gloves while fixing an electric switch?
Answer: Electricians wear rubber gloves to protect themselves from electric shocks because rubber does not conduct electricity.
Question 10: Why do tools like screwdrivers used by electricians have plastic or rubber handles?
Answer: The plastic or rubber handles protect the electrician from electric shocks because these materials don’t conduct electricity.