Question 1

Q1: Choose the incorrect statement. (i) A switch is the source of electric current in a circuit. (ii) A switch helps to complete or break the circuit. (ii...

Accepted Answer

The incorrect statement is (i): A switch is the source of electric current in a circuit. A switch only helps to complete or break the circuit, it is not the source of electric current. The electric cell or battery is the source of electric current.

Question 2

Q10: You are given six cells marked A, B, C, D, E, and F. Some of these are working and some are not. Design an activity to identify which of them are work...

Accepted Answer

(i) Items required:    Six electric cells (A, B, C, D, E, and F)    A small incandescent lamp    Connecting wires    A switch (optional) (ii) Procedure: 1.  Connect cell A to the lamp using connecting wires and a switch (if available). 2.  Close the switch (if used). Observe if the lamp glows. 3.  I...

Question 3

Q11: An LED requires two cells in series to glow. Tanya made the circuit as shown in Fig. 3.21. Will the lamp glow? If not, draw the wires for correct conn...

Accepted Answer

The lamp will not glow in the circuit shown in Figure 3.21 because the cells are not connected in series correctly. The positive terminal of one cell must be connected to the negative terminal of the other cell. In the given circuit, it appears the positive terminal of one cell is connected to the p...

Question 4

Q2: Observe Fig. 3.16. With which material connected between the ends A and B , the lamp will not glow?

Accepted Answer

The lamp will not glow when an insulator is connected between ends A and B. Insulators do not allow electric current to pass through them. Examples of insulators include rubber, plastic, and wood.

Question 5

Q3: In Fig. 3.17, if the filament of one of the lamps is broken, will the other glow? Justify your answer.

Accepted Answer

If the filament of one of the lamps is broken, the other lamp will not glow. This is because a broken filament creates an open circuit, interrupting the flow of electric current. For both lamps to glow, the circuit must be complete, allowing electric current to flow through both filaments.

Question 6

Q4: A student forgot to remove the insulator covering from the connecting wires while making a circuit. If the lamp and the cell are working properly, wil...

Accepted Answer

If the student forgot to remove the insulator covering from the connecting wires, the lamp will not glow. The insulator covering prevents the electric current from flowing through the wires, thus the circuit will not be completed.

Question 7

Q5: Draw a circuit diagram for a simple torch using symbols for electric components.

Accepted Answer

The circuit diagram for a simple torch includes an electric cell (represented by a long and short parallel line), a switch, a lamp (represented by a circle with a cross inside), and connecting wires. The positive terminal of the cell is connected to one end of the switch, and the other end of the sw...

Question 8

Q6: In Fig. 3.18: (i) If $\mathrm{S}_{2}$ is in ' ON ' position, $\mathrm{S}_{1}$ is in ' OFF ' position, which lamp(s) will glow? (ii) If $\mathrm{S}_{2}...

Accepted Answer

(i) If $S_2$ is in the 'ON' position and $S_1$ is in the 'OFF' position, only lamp $L_2$ will glow. (ii) If $S_2$ is in the 'OFF' position and $S_1$ is in the 'ON' position, only lamp $L_1$ will glow. (iii) If both $S_1$ and $S_2$ are in the 'ON' position, both lamps $L_1$ and $L_2$ will glow. (iv)...

Question 9

Q7: Vidyut has made the circuit as shown in Fig. 3.19. Even after closing the circuit, the lamp does not glow. What can be the possible reasons? List as m...

Accepted Answer

Possible reasons why the lamp does not glow even after closing the circuit include: 1.  The electric cell may be exhausted. 2.  The lamp may be fused (filament broken). 3.  The connections may be loose. 4.  The switch may be faulty. 5.  The wiring may be incomplete or broken. To find out why the lam...

Question 10

Q8: In Fig. 3.20, in which case(s) the lamp will not glow when the switch is closed?

Accepted Answer

The lamp will not glow in the following cases when the switch is closed: (a) If the circuit is incomplete, meaning there is no continuous path for the electric current to flow. (b) If the battery is connected incorrectly, such as positive to positive or negative to negative. (c) If the conducting wi...

Question 11

Q9: Suppose the '+' and '-' symbols cannot be read on a battery. Suggest a method to identify the two terminals of this battery.

Accepted Answer

To identify the positive and negative terminals of a battery without '+' and '-' markings, connect the battery to an LED. An LED has a longer wire (positive terminal) and a shorter wire (negative terminal). If the LED glows, the longer wire is connected to the positive terminal of the battery, and t...

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