A solar cell has a light-gathering area of 10 cm² and produces 0.2 A at 0.8 V (DC) when illuminated with S= 1 000 W/m² sunlight. What is the efficiency of the solar cell?

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A heater is placed in 5 liters of ethanol, which has a specific heat capacity of 2.44 joules per gram kelvin and a specific gravity of 0.7893. Assume the initial temperature of the ethanol is 70 degrees Fahrenheit, the heater is powered by a voltage of 240 volts at a current of 500 milliamperes, and the transfer of energy to the ethanol as heat has an efficiency of 45%. How long must the heater operate to raise the temperature of the ethanol to 95 degrees Fahrenheit? Express your answer in units of minutes.

(1) An incandescent light bulb produces 5.85 Joules of light energy each second. This bulb is 7.80% efficient, meaning that only 7.80% the total energy it consumes becomes light and the rest becomes waste heat. A 12.0 W fluorescent bulb is designed to produce the same illumination (in Joules of light energy per second) as the incandescent bulb. A large building uses 17,530 light bulbs. At a cost of 8.56€/kW-hr for electricity, how much money will the owners of the building save each year if they use fluorescent bulbs instead of incandescent bulbs? Express your answer in dollars. [answer: about $828,000]

A particular household uses a 1.9 kW heater 1.8 h/day ("on" time), four 100 W lightbulbs 6.0 h/day, a 2.8 kW electric stove element for a total of 1.0 h/day, and miscellaneous power amounting to 2.0 kWh/day. Part A If electricity costs $0.105 per kWh, what will be their monthly bill (30 d)? Express your answer using two significant figures. Cost = 33 $ per month Submit Previous Answers ✓ Correct Part B How much coal (which produces 7500 kcal/kg) must be burned by a 36 % -efficient power plant to provide the yearly needs of this household? Express your answer to two significant figures and include the appropriate units. O ΕΞΑ HÅ m= 100.97 kg Submit Previous Answers Request Answer ?

A ceramic capacitor has a value of C=10,000 pF. The capacitor consists of a dielectric disc between two paralell metal disc plates. The dielectric disc has a relative permittivity of 40 and a conductivity of 10-12 S/m. The diameter of the disc plates is 1 cm. The voltage across the plates is 100 V. Find the leakage current density in the dielectric in micro Amperes per square meter. Round off your answer to one decimal.

In recent years, practical hybrid cars have hit the road—cars in which the gasoline engine runs a generator that charges batteries that run an electric motor. These cars offer increased efficiency, but significantly greater efficiency could be provided by a purely electric car run by batteries that you charge by plugging into an electric outlet in your house.But there’s a practical problem with such vehicles: the time necessary to recharge the batteries. If you refuel your car with gas at the pump, you add 130 MJ of energy per gallon. If you add 20 gallons, you add a total of 2.6 GJ in about 5 minutes. That’s a lot of energy in a short time; the electric system of your house simply can’t provide power at this rate.There’s another snag as well. Suppose there were electric filling stations that could provide very high currents to recharge your electric car. Conventional batteries can’t recharge very quickly; it would still take longer for a recharge than to refill with gas.One possible…

At RM 0.218 Kilowatt-hour, how much it cost to leave a 6 W kitchen bulb on day and nightfor a 6 months period?

Detector A is 10 m from a light bulb. Detector A measures the power of the light bulb to be 100 W. Detector B is 20 m from the same bulb. What is the power of the light bulb according to detector B?

it the minimum average power? 13. An energy-efficient fluorescent lightbulb operating at power Pı = 28 W can produce the same level of brightness as a conventional incandescent lightbulb operating at power P, 100 W. Lifetime of the energy-efficient bulb is T = 10000 h, and its purchase price is B1 = $4.50. Lifetime of the conventional bulb is T2 = 750 h, and its purchase price is B2 = $0.42. Suppose electrical energy costs R = $0.20/kWh, i.e. 20 cents per kilowatt- hour. a) Calculate the total cost of using energy-efficient bulbs over 10,000 hours. b) Calculate the total cost of using conventional bulbs over 10,000 hours. Note that you must include both the cost of purchasing the bulbs and the cost of energy.