The atoms have changed over time. scientists think this is wrong. why?
a) the nucleus is the center of an atom
b) an atom is a solid material
c) electrons have a negative charge
d) electrons are arranged in layers

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?

Apulley system is used to lift a 2,000 newton engine up a distance of 3 meters. the operator must apply a force of 250 newtons to the chain of the pulley system to lift the motor. to lift the engine 3 meters, the operator must pull a total of 30 meters of chain through the pulley system. what is the value of di?

Brades exam guidelines exam instructions billing & payments & support question 6 of 20 : select the best answer for the question use this illustration to answer the question below. forms & resources al programs 9 ww linics 6. in the circuit shown in the figure above, suppose that the value of r, is 100k, and the value of r2 is 470 kq. at which of the following locations in the circuit would you measure the highest voltage with your meter? rvices 999999 a. between points b and c b. between points a and b c. between points b and e d. between points a and c eredu mark for review (will be highlighted on the review page) mend < < previous question next question