A long straight wire having uniform resistance per uni length `lamda` (ohms/metre) is bent into `V`-shape as shown (angle `DAC=alpha`). A uniform and constant magnetic field `B` (tesla) exists in space which is perpendicular to the plane of `V`- shaped wired. Another straight wire `EF` of same uniform resistance per unit length `lamda` (ohms/metre) is pulled with constant velocity `u` (m/s) such that the wire `EF` is always perpendicular to side `AD` of `V` -shape (the wire `EF` is always in conducitng contact with the `V`- shaped wire at two points).At `t=0` (`t` is the time is seconds) the value of `x=0` (`x=` distance of wire `EF` from end `A` in metres)
The magnetic force acting on the wire `EF` due to uniform magnetic field `B` at any time `t` (in `N`) is

Options

A. a. `(B^(2)tu^(2) tan^(2)alpha)/(lamda(1+tanalpha+secalpha))`
B. b. `(B^(2)u^(2)tan^(2)alpha)/(lamda(1+tanalpha+secalpha))`
C. c. `(B^(2)tu^(2))/(lamda(2+tan alpha))`
D. d. none of these

Explanation

NA