Chapter 21
1. (p.654 prob.7) (a) If the resistance of the resistor in Fig. 21-46 is slowly increased, what is the direction of the current induced in the small circular loop inside the larger loop? (b) What would it be if the small loop were placed outside the larger one, to the left?
2. (p.654 prob.10) The magnetic field perpendicular to a circular loop of wire 20cm in diameter is changed from +0.52T to -0.45T in 180ms, where + means the field points away from an observer and - toward the observer. (a) Calculate the induced emf. (b) In what direction does the induced current flow?
3. (p.655 prob.15) A single rectangular loop of wire with dimensions shown in Fig. 21-49 is situated so that part is inside a region of uniform magnetic field of 0.450T and part is outside the field. The total resistance of the loop is 0.230W. Calculate the force required to pull the loop from the field (to the right) at a constant velocity of 3.40m/s. Neglect gravity.
4. (p.655 prob.22) A simple generator has a 720-loop square coil 21.0cm on a side. How fast must it turn in a 0.650-T field to produce a 120-V peak output?
5. (p.656 prob.35) The output voltage of a 100-W transformer is 12V and the input current is 20A. (a) Is this a step-up or a step=down transformer? (b) By what factor is the voltage multiplied?