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Generators and Transformers Physics 106 1. Transformers Concepts: 2. Generators NBA sin t : The emf produced by coil of N turns and area A rotating in a magnetic field B with an angular frequency of ω. I 1V1 I 2V2 Equations: Transformer: N V V2 2 1 N1 1 Resonant frequency: f 0 2 LC Sample Problem Tesla: AC Edison: DC Transformer: A transformer on a pole near a factory steps the voltage down from 3,600 V to 120 V. The transformer is to deliver 1,000 kW to the factory at 90% efficiency. Find (a) the power delivered to the primary, (b) the current in the primary, and (c) the current in the secondary. In a model ac generator, a 500-turn rectangular coil, 8.0 cm by 20 cm, rotates at 120 rev/min in a uniform magnetic field of 0.60 T. a. What is the maximum emf induced in the coil? b. What is the instantaneous value of the emf in the coil at t = (π/32)s? Assume that the emf is zero at t = 0. c. What is the smallest value of t for which the emf will have its maximum value? Physics Hero Nikolai Tesla and his lightening machine. The basic function of the electric generator is which of the following conversion processes? Sample Exam Question a. mechanical energy to electrical b. electrical energy to mechanical c. low voltage to high or vice versa d. alternating current to direct A transformer consists of a 500-turn primary coil and a 2 000-turn secondary coil. If the current in the secondary is 3.00 A, what is the primary current? Sample Exam Question Don’t Worry About a. 0.750 A b. 1.33 A c. 12.0 A d. 48.0 A The Chapter on AC. Just skim it, look at the pictures and scan the equations. Pay attention to the forms of the equations: what is the same and what is different between the equations used for AC circuits and those you have been using for DC circuits? For example, the equation for AC Power still has the general form of Power I 2 R except with AC, the power is an 2 R. average and the current is a “root-mean-square”: Pav I rms