Q. 24.3( 24 Votes )

# Use Lenz’s law to determine the direction of induced current in the situations described by Fig. 6.19:

(a) A wire of irregular shape turning into a circular shape;

(b) A circular loop being deformed into a narrow straight wire.

Answer :

According to the Lenz’s law: The direction of induced current by change in magnetic field (Faraday’s induction) will be such that it opposes the change that caused it.

(a) In the figure given below, the direction of magnetic field is perpendicular into the paper.

Now, when we change the shape of irregular loop into a circular loop, then the area of the loop will increase. Because, area of circle is considered to be greatest.

Since, area of loop increases, ∴ the magnetic flux will also increase.

Now, the current will be induced in the loop such that the magnetic flux decreases. And, magnetic field will decrease when the area will decrease i.e. the wires should be pulled in the inwards directions, to decrease the net magnetic field.

∴ the current will be along “adcba”.

(b) In the figure given below, the direction of magnetic field is perpendicular coming out of the paper.

Now, when circular loop is transformed into a narrow straight wire, then the area of the loop will decrease. Since, area of loop decreases, ∴ the magnetic flux will also decrease.

Now, the current will be induced in the loop such that the net magnetic flux increases in the wire. ∴ the current flow will be along “adcba” which produces the induced magnetic field outwards the paper.

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