A metal crossbar of mass M rides on a pair of long, horizontal conducting rails separated by a distance ? and connected to a device that supplies constant current I to the circuit, as shown in Figure. A uniform magnetic field B is established as shown.

(a) If there is no friction and the bar starts from rest at t = 0, show that at time t the bar has velocity v = (BI ? /M)t.

(b) In which direction will the bar move?

(c) If the coefficient of static friction is ?s, find the minimum field B necessary to start the bar moving.

Transcribed Image Text:

B in Constant current source