NCERT Class VII Science Class: Chapter –14. Electric Current and its Effects – Part-3

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Question 7:

Will the compass needle show deflection when the switch in the circuit shown by Fig.14.24 is closed?

As showing in images is a electrical circuit

Electrical Circuit

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Answer:

No, the compass needle will not show deflection even though the switch is closed, because there is no source of electric current (Battery or cell). An electric cell or battery needs to be connected here. In the absence of electric current, there is no magnetic field produced by the wires. Hence there is no deflection.

Question 8:

Fill in the blanks:

  1. Longer line in the symbol for a cell represents its ____________ terminal.

  2. The combination of two or more cells is called a ____________.

  3. When current is switched ‘on’ in a room heater, it ____________.

  4. The safety device based on the heating effect of electric current is called a ____________.

Answer:

  1. Longer line in the symbol for a cell represents its positive terminal.

  2. The combination of two or more cells is called a battery.

  3. When current is switched ‘on’ in a room heater, it becomes hot.

  4. The safety device based on the heating effect of electric current is called a fuse.

Question 9:

Mark ‘T’ if the statement is true and ‘F’ if it is false:

  1. To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell. (T/F)

  2. When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. (T/F)

  3. An electromagnet does not attract a piece of iron. (T/F)

  4. An electric bell has an electromagnet. (T/F)

Answer:

  1. To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell. (False)

  2. When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. (True)

  3. An electromagnet does not attract a piece of iron. (False)

  4. An electric bell has an electromagnet. (True)

Question 10:

Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.

Answer:

An electromagnet is just like as a bar magnet and it can attract iron pieces only. Plastic does not have any magnetic property, so electromagnet cannot be used to separate plastic bags from garbage heap.