You place an ice cube in a microwave oven. If it requires 32,195 J to melt the ice cube and the oven delivers 97 W of power to the ice cube, determine the time (in min) needed to melt the ice cube. min

An electrical power plant has an overall efficiency of 15%. The plant is to deliver 150 MW of electrical power to a city, and its turbines use coal as fuel. The burning coal produces steam at 190C, which drives the turbines. The steam is condensed into water at 25C by passing through coils that are in contact with river water. (a) How many metric tons of coal does the plant consume each day (1 metric ton = 1 103 kg)? (b) What is the total cost of the fuel per year if the delivery price is 8 per metric ton? (c) If the river water is delivered at 20C, at what minimum rate must it flow over the cooling coils so that its temperature doesnt exceed 25C? Note: The heat of combustion of coal is 7.8 103 cal/g.

An engine absorbs three times as much heat as it discharges. The work done by the engine per cycle is 50 J. Calculate (a) the efficiency of the engine, (b) the heat absorbed per cycle, and (c) the heat discharged per cycle.

(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 ?