Check sibling questions

(i) A coil of insulated copper wire is connected to a galvanometer. What happens if a bar magnet is:

(a) Pushed into the coil?

(b) Withdrawn from inside the coil?

(c) Held stationary inside the coil? Give reasons for your observation.

 

Answer:

bar-magnet-pushed-inside-a-coil-of-copper gif

Galvanometer is a device which is used to check the presence of current in a circuit.

Since there is no battery connected in the circuit, the current that will be generated in the insulated copper wire is going to be induced current.

Current is induced when

  • Moving conducting Wire inside a Fixed Magnetic Field 
  • Keeping Conductor Fixed and Changing Magnetic Field

As bar magnet is

(i) pushed into the coil

The magnetic field around the coil would change.

Hence, some current will be induced in the coil.

Therefore, galvanometer will show some deflection.

 

(ii) withdrawn from inside the coil

The magnetic field around the coil would change.

Hence, some current will be induced in the coil.

Therefore, galvanometer will show some deflection, but in the opposite direction as that of Case (i).

 

(iii) held stationary inside the coil

Since the bar magnet is held stationary

The magnetic field around the coil remains constant.

Thus, the magnetic field does not change.

 

Hence, no current will be induced in the coil.

Therefore, galvanometer will show no deflection.

 

(ii) Mention one more method of inducing current in a coil.

Answer

We can induce current by

  • Moving the Conducting Wire inside a Fixed Magnetic Field
    Hence, if we keep a conducting wire near the magnetic field  of magnet and move it vigorously, current will be induced in it.
  • Keeping Wire (Conductor) Fixed and Changing Magnetic Field
    Hence, if keep a wire fixed and change poles of magnet vigorously, current will be induced in wire.
  • Changing current in a nearby coil
    If current is changed in a current carrying coil is placed near the conductor, magnetic field around it would change. Hence, current will be induced

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CA Maninder Singh is a Chartered Accountant for the past 12 years and a teacher from the past 16 years. He teaches Science, Accounts and English at Teachoo