Question

The adjacent diagram shows a movable permanent magnet and fixed copper coil of many turns, connected to a center zero galvanometer.

(a) Describe your observations when:

(i) the magnet is rapidly moved in the direction of the arrow.

(ii) the magnet is stopped within the coil.

(iii) the magnet is then pulled out rapidly

b) What will be your observations, if a more powerful magnet is used?

Answer 1

Step 1: Given data

Given a movable permanent magnet and fixed copper coil of many turns, connected to a center zero galvanometer.

Step 2: a) Observations on the given data for case (i)

(i) the magnet is rapidly moved in the direction of the arrow

1. When the magnet is rapidly moved in the direction of the arrow, the galvanometer shows deflection because the flux linkage is increasing.
2. When the magnet is rapidly moved in the direction of the arrow, the rate of change of magnetic flux increases which induces current in the circuit.

Step 3: Observations on the given data for case (ii)

(ii) the magnet is stopped within the coil.

1. When the magnet is stopped within the coil, there will be no change in the magnetic flux.
2. So, the galvanometer pointer comes back to the center zero position when the magnet stopped within the coil.

Step 4: Observations on the given data for case (iii)

(iii) the magnet is then pulled out rapidly

1. When the magnet is then pulled out rapidly, the galvanometer pointer shows deflection in opposite direction because now the flux linkage is decreasing.
2. When the magnet is pulled out rapidly, then the rate of change of magnetic flux again increases within the coil which induces current in the circuit but in opposite direction.

Step 5: b) Observations if a more powerful magnet is used

1. Magnetic field is directly proportional to the strength of the electric current.
2. If a more powerful magnet is used, the magnitude of induced emf increases. Then the deflection is more.
3. Therefore, if a more powerful magnet is used then the galvanometer deflects more.