3448

Physics Electromagnetic Induction Level: High School

A straight , horizontal wire of length l, mass M , and resistance R falls vertically without friction or air drag along parallel vertical conducting rails of negligible resistance , as shown (assume this wire remains in constant with the rails as it falls) . The rails are connected at the bottom by a horizontal rail (of zero resistance ) ,so that the wire and rails form a closed rectangular loop . A uniform horizontal field B perpendicular to the wire exists throughout the region . What is terminal velocity v of the wire , ie , the eventual steady-state speed reached by the wire ?

1) v = B2l/ M g

2) v = M g / B l

3) v = M g R / B2 l2

4) v = M g R2 / B2 l3

5) v = M g / B2 l

a) After a long time , what is the current I in the loop ?

b) What is the electrical power P produced in the loop after a long time ?

c) The power produced by gravity acting on the wire when it is falling at the terminal velocity is .

1) zero

2) equal to the electrical power .

3) greater than the electrical power .

4) less than the electrical power .

5) either greater or less than the electric power , depending on the magnitude of B .

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