Recall from high school that sine and cosine curves have the same basic shape, they are just shifted relative to one-another. Sine and cosine functions are collectively called "sinusoids" or "sinusoidal functions." For a reminder of how to sketch such the graphs of such functions, see

http://www.math.washington.edu/~m124/source/supps/week1/sinusoidal/sinusoidal.pdf

Sinusoidal functions have the form

y = A cos(kt c) + dor

y = A sin(kt c) + d

where A is the amplitude, c/k is the phase shift, 2 /k is the period (or wavelength), and d is the vertical shift.

Chapter 26 AC ElectricityFriday, January 14, 2011

10:03 AM

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CQ 3 Lightbulbs in AC circuits "flicker" in intensity, though the flickering is too fast for your eyes to sense it. If a light bulb is connected to a 120 V/60 Hz power supply, how many times a second does the bulb reach peak brightness?

CQ 1 Identical resistors are connected to separate 12 V AC sources. One source operates at 60 Hz, the other at 120 Hz. In which circuit, if either, does the resistor dissipate the greater average power?

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CP 3 A resistor dissipates 2.00 W when the rms voltage of the emf is 10.0 V. At what rms voltage will the resistor dissipate 10.0 W?

CP 5 A toaster oven is rated at 1600 W for operation at 120 V/60 Hz. (a) What is the resistance of the oven heater

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V/60 Hz. (a) What is the resistance of the oven heater element? (b) What is the peak current through it? (c) What is the peak power dissipated by the oven?

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CP 11 A power pack charging a cell phone battery has an output of 0.40 A at 5.2 V (both rms). Determine the rms current at the 120 V/60 Hz wall outlet where the power pack is plugged in.

CP 13 The "power cube" transformer for a portable CD player has an output of 4.5 V and 600 mA (both rms) when plugged into a 120 V/60 Hz outlet. (a) If the primary coil has 400 turns of wire, how many turns are on the secondary coil? (b) What is the peak current in the primary coil?

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CP 53 A 15-km-long, 230 kV aluminum transmission line

delivers 34 MW to a city. If we assume a solid cylindrical cable, what minimum diameter is needed if the voltage decrease along this run is to be no more than 1.0% of the transmission

voltage? The resistivity of aluminum is 2.7 × 10-8 Ω m.

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CP 15 A typical North American family uses 1000 kWh of electricity per month. (a) Determine the average rms current in the 120 V power line to the house. (b) On average, what is the resistance of the active circuits in a household?

CP 17 The following appliances are connected to a single 120 V, 15 A circuit in a kitchen: a 330 W blender, a 1000 W coffee pot, a 150 W coffee grinder, and a 750 W microwave oven. If

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pot, a 150 W coffee grinder, and a 750 W microwave oven. If these are all turned on at the same time, will they trip the circuit breaker?

CP 19 Suppose you leave a 110 W television and two 100 W lightbulbs on in your house to scare off burglars while you go out dancing. If the cost of electric energy in your town is $0.12/kWh and you stay out for 4.0 hours, how much does this robbery-prevention measure cost?

CP 21 If you touch the terminal of a battery, the small area of contact means that the skin resistance will be relatively large; 50 kΩ is a reasonable value. What current will pass through your body if you touch the two terminals of a 9.0 V battery with your two hands? Will you feel it?

also see http://amasci.com/amateur/whygnd.html

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Will it be dangerous?

CP 25 A bird is perched on a high-voltage transmission wire. The transmission wire is 100 km long, has a resistance of 7.0 Ω, and carries a current of 200 A. If the bird's feet are 2.0 cm apart, what is the potential difference between the bird's feet?

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