Selina solutions

Selina solutions

Grade 7

Electricity and Magnetism | Short/Long Answer Questions

Question 12

Q12) Draw a labelled diagram to make a soft iron bar as an electromagnet. Describe in steps the procedure.

Solution:

The electromagnets are made in two shapes

  1. Bar shaped or I magner
  2. Horseshoe or U shaped
  3. To make I shaped electromagnet we first soft iron bar PQ and wind a thin insulated copper wire around the bar. Connect a cell or a battery B and a key K in series between the ends of the coil.

When key K is closed, current passes through the winding of the coil and the bar becomes a magnet. As the key K is opened, the current stops flowing in the coil and the bar loses its magnetism. Thus, the bar behaves like an electromagnet.

  1. To make a U shaped electromagnet we take a U shaped soft iron piece. Wind a thin insulated copper wire on its arms such that the winding in the two arms is in the opposite direction. In figure winding in the arm A starts from the front and is in clockwise direction when seen from the bottom.

On reaching the upper end of the arm A, winding starts from the back at the top of the arm B and is in an anticlockwise direction. Connect a battery B and a key K between the two ends of the wire.

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subject-cta

Question 12

Q12) Draw a labelled diagram to make a soft iron bar as an electromagnet. Describe in steps the procedure.

Solution:

The electromagnets are made in two shapes

  1. Bar shaped or I magner
  2. Horseshoe or U shaped
  3. To make I shaped electromagnet we first soft iron bar PQ and wind a thin insulated copper wire around the bar. Connect a cell or a battery B and a key K in series between the ends of the coil.

When key K is closed, current passes through the winding of the coil and the bar becomes a magnet. As the key K is opened, the current stops flowing in the coil and the bar loses its magnetism. Thus, the bar behaves like an electromagnet.

  1. To make a U shaped electromagnet we take a U shaped soft iron piece. Wind a thin insulated copper wire on its arms such that the winding in the two arms is in the opposite direction. In figure winding in the arm A starts from the front and is in clockwise direction when seen from the bottom.

On reaching the upper end of the arm A, winding starts from the back at the top of the arm B and is in an anticlockwise direction. Connect a battery B and a key K between the two ends of the wire.

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subject-cta
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