A constant force `F` is being applied on a rod of length `t` kept at rest on two parallel conducting rails connected at ends by resistance `R` in uniform magnetic field `B` as shown.

Options

A. Th thermal power dissipated in the resistor is equal to rate of work done by externl person pulling the rod.
B. If applied external force is doubled then a part of external power increases the velocity of rod.
C. Lenz's Law is not satisfied if the rod is accelerated by external force
D. If resistance R is doubled then power required to maintain the constant velocity `v_(0)` becomes half.

Answer

A, B, D

Explanation

As long as the rod moves at a constant speed, all the work done by external person the rod is dissipated as heat in the resistor. As per Work-energy theorem, there is no change in kinetic energy of rod.
Here, force applied by external agent is `F=`BIl.
However, if applied external force is doubled then a part of external power increases the velocity of rod the rest is dissipated as heat.
Obviously, Lenz's law is not satisfied under such circumstances. Further, `P=E^(2)//R=B^(2)l^(2)//R`. Thus, if resistance R is doubled then power required to maintain the constant velocity `v_(0)` becomes half.