Which of these energy transformations best describes the overall operation of a hydroelectric power plant?
A) grav E ? therm E
B) thermal E ? electromag E
C) chem E ? electromag E
D) grav E ? electromag E
E) electromag E ? grav E
D
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Ideal Gas Law: A gas-filled vertical cylinder, closed at the bottom end, is fitted at the top with a piston that can move freely. The mass of the piston is 10.0 kg, and the initial height of the piston above the bottom of the cylinder is 25 cm. A mass of 8.0 kg is placed on the piston. What is the resulting height of the piston, assuming that the temperature of the ideal gas is kept constant?
A. 12 cm B. 13 cm C. 14 cm D. 15 cm E. 16 cm
A light-emitting diode (LED) converts electricity to approximately sinusoidal electromagnetic waves with a definite frequency f. Imagine that light from the LED creates an oscillating electric field with amplitude E0 at a certain location. If we increase the electrical power to the LED so that the oscillation amplitude is now 2E0, by what factor have we increased the power?
A. 4 times
B. 2 times
C. 
times
D. One cannot answer without more information.
A 120-V rms voltage at 60 Hz is applied across a 20-?F capacitor and an unknown resistor. If the rms value of the current in that circuit is 0.60 A, what is the value of the resistor?
A) 60 ? B) 120 ? C) 180 ? D) 150 ? E) 200 ?
Which of these did Count Rumford demonstrate?
a. That heat was only generated by fire, light, and sunshine. b. That caloric, or heat fluid, is a gas. c. That heat is a substance found in fire that is available only in limited amounts in every object. d. That heat can be generated in any amount wanted and was therefore not a material substance. e. That heat is a form of energy.