Bar cd is balanced under the action of * * * point force. Fcd=mgsin30？ ②

Substitute the data of ① and ② to get the solution? I= 1A, the direction is determined by the right hand, from D to C.

(2) Is the ampere force on the rod ab equal to the ampere force on the rod cd? Fab=Fcd

Is there any force balance on the ab bar? F=mgsin30 +IlB

Substitute the data to get the solution? F=0.2N

(3) given time t, the heat generated by the rod cd is Q=0. 1J, which is known from Joule's law? Q=I2Rt

Assuming that the speed of uniform motion of ab rod is V, what is the induced electromotive force? E=Blv？

From ohm's law of closed circuit? I=E2R

In time t, the displacement of ab rod along the guide rail? x=vt？

The work done by force f? W=Fx？

Combining the above, substitute the data to get the solution? W=0.4J

Answer: (1) The current I passing through the cd rod is 1A and the direction is D → C. 。

(2) The force f on the 2)ab rod is 0.2N 。

(3) The work W done by the rod force F is 0.4J J. 。