Two 1.50-v batteries—with their positive terminals in the same direction—are inserted in series into the barrel of a flashlight. one battery has an internal resistance of 0.240 ω, the other an internal resistance of 0.180 ω. when the switch is closed, a current of 600 ma occurs in the lamp. (a) what is the bulb's resistance? ω (b) what fraction of the chemical energy transformed appears as internal energy in the batteries? %

Aheat engine running backward is called a refrigerator if its purpose is to extract heat from a cold reservoir. the same engine running backward is called a heat pump if its purpose is to exhaust warm air into the hot reservoir. heat pumps are widely used for home heating. you can think of a heat pump as a refrigerator that is cooling the already cold outdoors and, with its exhaust heat qh, warming the indoors. perhaps this seems a little silly, but consider the following. electricity can be directly used to heat a home by passing an electric current through a heating coil. this is a direct, 100% conversion of work to heat. that is, 19.0 \rm kw of electric power (generated by doing work at the rate 19.0 kj/s at the power plant) produces heat energy inside the home at a rate of 19.0 kj/s. suppose that the neighbor's home has a heat pump with a coefficient of performance of 4.00, a realistic value. note: with a refrigerator, "what you get" is heat removed. but with a heat pump, "what you get" is heat delivered. so the coefficient of performance of a heat pump is k=qh/win. an average price for electricity is about 40 mj per dollar. a furnace or heat pump will run typically 200 hours per month during the winter. what does one month's heating cost in the home with a 16.0 kw electric heater? what does one month's heating cost in the home of a neighbor who uses a heat pump to provide the same amount of heating?

If you divide a speed in miles per minute by 60, you get the same speed expressed in miles

Use henry's law and the solubilities given below to calculate the total volume of nitrogen and oxygen gas that should bubble out of 1.7 l of water upon warming from 25 ˚c to 50 ˚c. assume that the water is initially saturated with nitrogen and oxygen gas at 25 ˚c and a total pressure of 1.0 atm. assume that the gas bubbles out at a temperature of 50 ˚c. the solubility of oxygen gas at 50 ˚c is 27.8 mg/l at an oxygen pressure of 1.00 atm. the solubility of nitrogen gas at 50 ˚c is 14.6 mg/l at a nitrogen pressure of 1.00 atm. assume that the air above the water contains an oxygen partial pressure of 0.21 atm and a nitrogen partial pressure of 0.78 atm.