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Unformatted text preview: 21.38. Set Up: Example 21.10 shows that the inductance of a toroidal solenoid is Solve: 21.39. Set Up: Problem 21.37 shows that for a long solenoid Solve: 21.40. Set Up: A transformer transforms voltages according to The effective resistance of a secondary circuit of resistance R is and Solve: (a) (b) 21.41. Set Up: A transformer transforms voltages according to The effective resistance of a secondary circuit of resistance R is Resistance R is related to P and V by Conservation of energy requires so Solve: (a) and we want so use a step-down transformer with (b) so (c) The resistance R of the blower is The effective resistance of the blower is Reflect: Energy is provided to the primary at the same rate that it is con- sumed in the secondary. Step-down transformers step up resistance and the current in the primary is less than the cur- rent in the secondary. 21.42. Set Up: For an ideal transformer, Solve: (a) (b) (c) (d) so 21.43. Set Up: and Solve: (a) (b) (c) Reflect: Since the power supplied to the primary must equal the power delivered by the secondary, in a step-up...
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- Spring '07