A hydroelectric power plant operates at its rated power of 7 MW. If the plant has produced 26 million kWh of electricity in a specified year, determine the number of hours the plant has operated that year. 2893 hours 1125 hours 8760 hours 2460 hours O 3714 hours

(a) What is the available energy content, in joules, of a battery that operates a 2.00-W electric clock for 18 months? (b) How long can a battery that can supply 8.00104 J run a pocket calculator that consumes energy at the rate of 1.00103 ?

(a) What is the average power consumption in watts of an appliance that uses 5.00 kW h of energy per day? (b) How many joules of energy does this appliance consume in a year?

Review A system consists of a planet and a star, with the planet in an elliptical orbit. As the planet orbits, which of these quantities change because they depend on the mass of the planet? Explain your answers. a. Gravitational potential energy b. Gravitational potential c. Kinetic energy d. Gravitational force e. Gravitational field

A 120.-V motor has mechanical power output of 2.50 hp. It is 90.0% efficient in converting power that it takes in by electrical transmission into mechanical power. (a) Find the current in the motor. (b) Find the energy delivered to the motor by electrical transmission in 3.00 h of operation. (c) If the electric company charges 0.110/kWh, what does it cost to run the motor for 3.00 h?

(a) Calculate the power per square meter reaching Earth's upper atmosphere from the Sun. (Take the power output of the Sun to be 4.001026 W.) (b) Part of this is absorbed and reflected by the atmosphere, so that a maximum of 1.30 kW/m2 reaches Earth's surface. Calculate the area in km 2 of solar energy collectors needed to replace an electric power plant that generates 750 MW if the collectors convert an average of 2.00% of the maximum power into electricity. (This small conversion efficiency is due to the devices themselves, and the fact that the sun is directly overhead only briefly.) With the same assumptions, what area would be needed to meet the United States' energy needs (1.051020J) ? Australia's energy needs (5.41018J) ? China's energy needs (6.31019J) ? (These energy consumption values are from 2006.)

What would be the maximum cost of a CFL such that the total cost (investment plus operating) would be the same for both CFL and incandescent 60-W bulbs? Assume the cost of the incandescent bulb is 25 cents and that electricity costs 10 cents/kWh, Calculate the cost for 1000 hours, as in the cost effectiveness of CFL example.

Suppose you need to measure the potential difference between the points in Figure P29.4. Assume the voltmeter reading is the potential difference between the two leads: V = Vred Vblack. For each of the following measurements, determine at which point you would connect the red lead and at which point you would connect the black lead: a. Vb Va. b. Vc Vb. c. Vd Vc. d. Va Vd. FIGURE P29.4 Problems 4, 5, and 6.

A person in good physical condition can put out 100 W of useful power for several hours at a stretch, perhaps by pedaling a mechanism that drives an electric generator. Neglecting any problems of generator efficiency and practical considerations such as resting time: (a) How many people would it take to run a 4.00-kW electric clothes dryer? (b) How many people would it take to replace a large electric power plant that generates 800 MW?

-gauge copper wire has a diameter of 9.266 mm. Calculate the power loss in a kilometer of such wire when it carries 1.00102 A.