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Unformatted text preview: song (shs546) Homework 16 weathers (22202) 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 4) 10.0 points A rectangular loop with resistance R has N turns, each of length L and width W as shown in the figure. The loop moves into a uniform magnetic field B (out of the page) with speed v . B B B B x a c b d L W v R B B B B x a c b d v What is d total dt (the time derivative of the flux for all turns of the loop) just after the front edge (side ab ) of the loop enters the field? 1. d total dt = B W L v 2. d total dt = B W v 3. d total dt = N B W L v 4. d total dt = N B W 5. d total dt = N B L 6. d total dt = N B W v correct 7. d total dt = N B L v 8. d total dt = N B W L 9. d total dt = zero 10. d total dt = B L v Explanation: = vector B vector A total = N = N [ vector B vector A ] The magnetic flux is given by total = N ( B A ) , where N and B are constant, but the area is changing. A = W ( v t ) initially, so total = N B W v t d total dt = N B W v . 002 (part 2 of 4) 10.0 points What is the direction of the current I in the loop just after it enters the magnetic field? 1. clockwise correct 2. No current 3. counter-clockwise Explanation: Apply Lenz Law, that is the induced cur- rent is in the direction that will generate a magnetic field that will oppose the change in flux. As more of the loop enters the field re- gion it picks up more flux out of the page, hence the induced current should generate an opposite field. Applying the right hand rule, the current must be clockwise. 003 (part 3 of 4) 10.0 points Given: I is the current as found in Part 2. What is the magnitude of the force F on the loop just after the front edge (side ab ) of the loop enters the field? song (shs546) Homework 16 weathers (22202) 2 1. bardbl vector F bardbl = N 2 W 2 R v B 2 2. bardbl vector F bardbl = N 2 B 2 W R v 3. bardbl vector F bardbl = zero 4. bardbl vector F bardbl = N 2 B 2 W v R 5. bardbl vector F bardbl = N 2 B 2 W 2 L v R 2 6. bardbl vector F bardbl...
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