NCERT Class VII Science Class: Chapter – 14. Electric Current and Its Effects – Part-3 (For CBSE, ICSE, IAS, NET, NRA 2022)

Get unlimited access to the best preparation resource for CBSE/Class-7 : get questions, notes, tests, video lectures and more- for all subjects of CBSE/Class-7.

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

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.

Developed by: