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posted by  belen on 7/24/2008 9:45:57 PM  |  status: Live  

I need help badly with this one question

Course Textbook Chapter Problem
General Physics N/A N/A N/A
Question Details:
The figure shows a zero-resistance rod sliding to the right on two zero-resistance rails separated by the distance L = 0.47 m. The rails are connected by a 13.7 resistor, and the entire system is in a uniform magnetic field with a magnitude of 0.750 T.

(a) Find the force that must be exerted on the rod to maintain a constant current of 0.125 A in the resistor.
mN
(b) What is the rate of energy dissipation in the resistor?
mW
(c) What is the mechanical power delivered to the rod?
mW

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posted by hanu on 7/25/2008 12:25:13 AM  |  status: Live
Asker's Rating: Lifesaver   
Response Details:
 
 
            Given that the  lenght of the rod is  L = 0.47 m
                      the resistanc of the circuit is R = 13.7 Ω
                      magnetic field strength is  B = 0.750 T
 ----------------------------------------------------------------------------
 
          Due to induced current in the circuit   the force  is F =  BIL       (along  V vector )
                                                                                        = (0.750 T)(0.125A)(0.47m)
                                                                                        = --------- N
            the rate of energy dessipated  in the resister is  H/t = I2R
                                                                                        = (0.125A)2(13.7Ω) 
                                                                                        = ---------  Joule/sec (or)W
         if the rod is moving in the magnetic field then the  induced emf is
                              ε = IR = BLv
                              v = IR /BL
               power delecered to the rod is  P =   F*V
                                                                 =  F*I*R /BL
                                                                 = ------ W 
                                                           
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