Integrated Concepts (a) What is the cost of heating a hot tub containing 1500 kg of water from 10.0C to 40.0C , assuming 75.0% efficiency to account for heat transfer to the surroundings? The cost of electricity is 9 cents/kW h . (b) What current was used by the 220-V AC electric heater, if this took 4.00 h?
Week 5 ch 4 notes Monday before the test ● Telescopes - modern astronomy ○ Photography opened door to modern astronomy ■ Permanent images of celestial objects ■ Astronomers able to see objects that were too faint or too close together ○ Help us learn ■ Collect more light than our eyes ● Light-collecting area ■ More detail than our eyes ● Angular resolution ■ Detect light invisible to the eye ● Ex. infrared, ultraviolet ○ Bigger is better ■ Larger light-collecting area is better ○ Smaller is better ■ Smaller angular resolution is better ● Angular resolution ○ Minimum a ngular separation that the telescope can distinguish ○ Basic telescope design ■ Refracting: lenses ● Focus light ■ Reflecting: mirrors ● Primary and secondary mirror ● Light bounces off mirrors to focus ● Tend to be shorter than refracting telescopes ● Often used for research ○ Radio waves and radio telescopes ■ Radio waves have wavelength ■ 1 centimeter to 10 meters, so large collecting area needed ■ Radio telescopes are typically tens of meters in diameter ○ Why we put telescopes in space ■ Not because they are closer to