What kind of electronic component is an led (light emitting diode)?

James is trying to prove newton's 2nd law of motion. he tries to move four different objects with different masses, shapes, and sizes from point a to point b. the objects are a toy car, a car, a refrigerator, and a kitchen table. after some experimentation, he finds that force is dependent on the mass of the object, rather than it's size or shape. the object that takes the most force to move is the

Imagine you are standing in the antarctic during the southern hemisphere summer. the sky is clear and blue. there are no clouds in the sky. your shadow is cast on the icy ground. what is the color of the shadow?

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?