Fig. shows a rectangular conducting loop PQSR in which arm RS of length l is movalbe. The loop is kept in a uniform magnetic field B directed downwards perpendicular to the plane of the loop. The arem RS is moved with a uniform speed v. Deduce an expression for
(i) the emf induced across the are RS.
(ii) the external force required to move the arm, and
(iii) the power dissipated as heat.

Explanation

Eddy current : Eddy currents are the currents induced in the bulk pieces of conductors when the amount of magnetic flux linked with the conductor changes.
Applications : (i) Eddy current is used in designing dead beat galvanometers.
(ii) Eddy currents are used in deep heat treatment of the human body.
(b) (i) The emf induced across the arm RS is `e Blv`
(ii) External force required is `F=BIl`
(iii) The power dissipated as heat is `P=I^(2) r=((B//v)/r)^(2) r=(B^(2) l^(2) v^(2))/r`
where r be the resistance of movable arm PQ of the rectangula rconductor.