To Electricity: Circuits and Their Components 7th Class

Electric Circuits – Q & A

(Designed for Class 6 – simple words, about 20 words per answer)

1. Choose the incorrect statement.

1. A switch is the source of electric current in a circuit.
2. A switch helps to complete or break the circuit.
3. A switch helps us to use electricity as per our requirement.
4. When the switch is “OFF”, there is an air gap between its terminals.

Answer : Statement (i) is incorrect. A switch merely opens or closes the path; the cell or battery supplies the actual current.

2. Observe Fig. 3.16. With which material connected between A and B will the lamp not glow?

Answer : The lamp stays dark if an insulator, like dry wood, plastic scale, or a rubber eraser, bridges A and B, blocking current.

3. In Fig. 3.17, if the filament of one lamp is broken, will the other glow? Justify.

Answer : No. Both lamps are in series; a broken filament breaks the sole path, so no current reaches the second lamp.

4. A student forgot to strip the plastic covering from connecting wires. Will the lamp glow? Explain.

Answer : It will not glow because the unstripped insulation prevents metal contact, leaving the circuit open and stopping current flow.

5. Draw a circuit diagram for a simple torch using symbols for electric components.

Answer : Draw two cells in series, then a switch symbol, then a bulb symbol, and finally return the wire to the cell’s negative terminal.

6. In Fig. 3.18, identify which lamps glow in each case.

1. S₁ ON, S₂ OFF
2. S₁ OFF, S₂ ON
3. S₁ ON, S₂ ON
4. S₁ OFF, S₂ OFF

Answer :

• (i) None will glow because the circuit is open at S₂, preventing current flow to the lamps.
• (ii) None will glow because S₁ is open, so the path is incomplete and current never reaches the lamps.
• (iii) Both lamps glow because S₁ and S₂ are closed, completing the circuit for current to pass.
• (iv) None glow because both switches are open, breaking the circuit at two points and blocking all current.

7. Vidya’s circuit (Fig. 3.19) closes but the lamp does not glow. List possible reasons.

Answer : Possible issues include exhausted or reversed cell, fused filament, loose or corroded connections, or a faulty switch; test every part separately with a fresh bulb and battery.

8. In Fig. 3.20, when will the lamp not glow after closing the switch?

Answer : The lamp fails to glow in arrangement (c) because the LED polarity is reversed, so current cannot flow through its junction.

9. A battery’s poles are unmarked. How can we identify the positive and negative terminals?

Answer : Connect the unknown cell to an LED through a 1 kΩ resistor; the LED lights only when its anode touches the positive end.

10. Cells A–F: some work, some do not. Design an activity to find the working ones.

Answer : Build a simple tester using a bulb holder, two wires, and a switch. Insert each cell, close the switch; cells lighting the bulb are good, the rest are dead.

11. An LED needs two cells in series to glow. Tanya’s cells are parallel. Will the lamp glow? Draw correct wiring.

Answer : It will not glow because both cells are parallel. Place cells in series—positive of the first to negative of the second—then connect the LED across the free ends.