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Q1. Consider the three statements about the standard symbol of a switch.
I. In the 'ON' symbol the line joining the two open circles is unbroken.
II. In the 'OFF' symbol the line joining the two open circles is shown tilted upward, leaving a clear gap.
III. The same symbol is used for both 'ON' and 'OFF' positions.
Which of these statements are correct?
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Q2. In Fig. 3.18 the lamps L1 and L2 are connected in series with switch S1 in the main loop and switch S2 between L1 and L2. With S1 in 'OFF' position and S2 in 'ON' position, which lamp(s) will glow?
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Q3. In Fig. 3.20 four single-loop circuits are drawn. The switch is shown closed in each. In which case will the lamp/LED definitely NOT glow?
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Q4. While making a circuit, a student forgot to remove the insulating covering from the connecting wires. The cell, lamp and switch are all in good working condition. What will be observed when the switch is in the ON position?
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Q5. In the circuit of Fig. 3.17 two incandescent lamps are connected in a single series loop with a battery. If the filament of one of the lamps breaks while the circuit is closed, the other lamp will
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Q6. An LED needs two cells in series to glow. Tanya's two cells are placed correctly so the battery's positive terminal is on the right, but the LED's longer wire is connected to the left side of the battery. The LED does NOT glow. What single change will make it glow?
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Q7. Consider four statements about a switch in a torch circuit:
(i) A switch is the source of electric current.
(ii) A switch completes or breaks the circuit.
(iii) A switch helps us use electricity as required.
(iv) When 'OFF', an air gap exists between its terminals.
Which is INCORRECT?
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Q8. Assertion (A): Electrical wires used in homes are covered with plastic or rubber.
Reason (R): Plastic and rubber are good conductors of electricity.
Which of the following is correct?
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Q9. Assertion (A): A person must never touch a household switch or plug with wet hands.
Reason (R): Our body is a conductor of electricity and current passing through the body may cause severe injury.
Which of the following is correct?
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Q10. An LED requires two cells joined in series to glow. Asha has connected it as in Fig. 3.21 — both cells are in the holder, but their orientations are not in the proper battery order. The LED does not glow. Which of these is the most likely reason?
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Q11. Read the three statements about a circuit diagram.
I. A circuit diagram represents the components of an electrical circuit using standard symbols.
II. Circuit-diagram symbols are decided independently by every teacher, with no international standard.
III. Standardising symbols across the world is the work of bodies such as IEC, ANSI and IEEE.
Which of these statements are correct?
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Q12. Table 3.1 lists six arrangements of one cell and one incandescent torch lamp. The lamp glows only in two of them. From the chapter's discussion, the lamp glows in those arrangements because
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Q13. In Activity 3.11, students touch the free ends of a tester to various household objects. Based on Table 3.3, which set is correctly classified as conductors of electricity?
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Q14. Read the three statements about the current supplied to electrical devices.
I. Electricity from batteries usually powers small devices and is of a type called Direct Current (DC).
II. The electricity from power plants that comes to the wall socket is called Alternating Current (AC).
III. AC can run larger appliances such as a refrigerator or air-conditioner.
Which of these statements are correct?
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Q15. Vidyut closed the switch in Fig. 3.19, but the lamp does not glow. Consider three possible reasons:
I. The filament of the lamp is broken (fused).
II. Plastic covering on the wires was not removed at the joints.
III. The cell is discharged.
Which reasons does the chapter accept?
