The electron’s path while in the region of magnetic field is a quarter circle. Show that the

time the electron spends in the region of magnetic field is 7.5×10⁻¹¹s.

A square loop of conducting wire is placed near a straight wire carrying a constant current I. The wire is in the same plane as the loop.

The loop is made to move with constant speed v towards the wire.

(i) Explain, by reference to Faraday’s and Lenz’s laws of electromagnetic induction, why work must be done on the loop.

(ii) Suggest what becomes of the work done on the loop.

\(t = \frac{1}{4}\frac{{2\pi  \times 4.5 \times {{10}^{ - 4}}}}{{9.4 \times {{10}^6}}}\);
=7.5×10⁻¹¹s 

(i) the flux in the loop is changing and so (by Faraday’s law) an emf will be induced in the loop;
(by Lenz’s law) the induced current will be (counter-clockwise) and so there will be a magnetic force opposing the motion;
requiring work to be done on the loop;

(ii) it is dissipated as thermal energy (due to the resistance) in the loop / radiation;