CBSE NCERT Class VII (7th) | Science
Chapter 14 : Electric Current and Its Effects
CBSE NCERT Solved Question Answer
Question: 1 - Draw in your notebook the symbols to represent the following components of electrical circuits: connecting wires, switch in the ‘OFF’ position, bulb, cell, switch in the ‘ON’ position, and battery.
Question: 2 - Draw the circuit diagram to represent the circuit shown in the following figure.
Question: 3 - The following figure shows four cells fixed on a board. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells.
Question: 4 - The bulb in the circuit shown in the following figure does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.
Answer: The positive terminals of both the cells are together and that is why the bulb is not glowing. The cells should be kept in a way that the positive terminal of one cell is near the negative terminal of another cell; to make the bulb glow.
Question: 5 - Name any two effects of electric current.
Answer: The two effects of electric current are; heating effect and magnetic effect.
Question: 6 - When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.
Answer: This happens because when electric current passes through a conducting wire, a magnetic field is created around the wire. The magnetic field causes deflection in the magnetic compass.
Question: 7 - Will the compass needle show deflection when the switch in the circuit shown by following figure is closed?
Question: 8 - Fill in the blanks:
- Longer line in the symbol for a cell represents its …………..terminal.
- The combination of two or more cells is called a ……………
- When current is switched ‘on’ in a room heater, it ……………….
Answer: heats up
- The safety device based on the heating effect of electric current is called a ……………
Answer: Electric fuse
Question: 9 - Mark ‘T’ if the statement is true and ‘F’ if it is false:
- To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell. (F)
- When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. (T)
- An electromagnet does not attract a piece of iron. (F)
- An electric bell has an electromagnet. (T)
Question: 10 - Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.
Answer: Since plastic is a non-magnetic material, so electromagnet cannot be used to separate plastic bags from a garbage heap.
Question: 11 - An electrician is carrying out some repairs in your house. He wants to replace a fuse by a piece of wire. Would you agree? Give reasons for your response.
Answer: A special wire with low melting point should be used for the fuse wire and any other wire would not serve the purpose. Hence, I would not agree with the electrician.
Question: 12 - Zubeda made an electric circuit using a cell holder shown in Fig. 14.4 (in the chapter), a switch and a bulb. When she put the switch in the ‘ON’ position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.
Answer: There can following possibilities:
- The terminals of cells are not in correct position.
- The connections are loose.
- The bulb may have fused.
Question: 13 -In the circuit shown in the following figure:
- Would any of the bulb glow when the switch is in the ‘OFF’ position?
Answer: None of the bulbs would glow.
- What will be the order in which the bulbs A, B and C will glow when the switch is moved to the ‘ON’ position?
Answer: All the bulbs would glow at once.
Chapter Summary : Electric Current and Its Effects