EXAM 1
Kevin lives next to a coal fired power plant. He wants to be greener, so he buys an electric vehicle, which he charges with his home's electricity. Is Kevin helping the environment?
No, the process efficiency and carbonized power grid make Kevin's EV dirtier than an IC (internal combustion) vehicle.
What transformation occurs in the Sun?
Nuclear to radiation
What is the biggest use of energy in a home?
heating and air conditioning
Where do you think coal comes from?
humic swamps millions of years ago
What energy growth rate per year would increase world energy use by 400% (2 doubling periods) in 80 years?
1.7% per year
The Penn State natural gas plant produces 7 MW of power. If it runs at 70% efficiency and has 7MW Power Out, what is the rate of energy input?
10 MW
A wind turbine costs $10 million to construct and generates $1 million worth of electricity per year. When has the wind turbine paid for itself (what is the pay-back period)?
10 years
Kevin wants to use less fossil fuel by purchasing an electric vehicle. EV's are currently about 50% efficient. The grid is about 20% efficient and Kevin's EV is about 50% efficient. What is the total efficiency of this process?
10%
It took 100 kJ of coal to produce the 15 kJ of useful energy in your home. What is the total efficiency?
15%
If you have 200 lbs of coal in your shed and you burn 1 lb a day, how long will it last?
200 days
What transformation occurs in a computer?
Electrical to light/sound
A steel rod is initially very cold. If it is placed close to a fire, what happens?
The steel rod heats up.
Some outdoor security lights are kept on overnight - 6 hours. They use 269 watts of power (figure out how much energy do they consume). If electricity costs $.10 per kilowatt hour, what is the electricity cost for these lights? Please include two decimal places in your answer.
0.16
A power plant consumes 100 MJ of Energy, of which only 24 MJ are wasted heat. What is the efficiency?
0.76
Match the following types of energy with the correct application
1. Chemical energy - A barrel of oil 2. Thermal energy - The sun beating down on a solar panel 3. Mechanical energy - A piston moving in a car engine
Match the scenario with the conversion between energy forms involved.
1. Electrical to Chemical - A cell phone is plugged in overnight and its battery is recharged. 2. Kinetic to Potential - A power company pumps water from a river up into a mountain lake. 3. Chemical to Heat - I eat a bagel and fall asleep for nine hours. 4. Heat to Chemical - A lab attendant cooks up a batch of a chemical compound. 5. Potential to Kinetic - A bowling ball descends from the top of the back-swing and contacts the floor smoothly. 6. Chemical to Electrical - A battery supplies the electricity to spin the motor in an electric toothbrush. 7. Kinetic to Electrical - The spinning armature in a generator pushes electrons through a wire. 8. Kinetic to Heat - The pads in a car's disk brakes slow the car and get hot. 9. Heat to Kinetic - Very hot, high pressure steam spins a turbine. 10. Radiant to Chemical - A plant's leaf makes sugar in the afternoon. 11. Heat to Radiant - A star shines in space.
Heat energy spontaneously migrates from areas of higher temperature to areas of lower temperature. Match each method of heat transfer with its description.
1. Heat flows from warmer to cooler by contact between the materials. The hot coffee heats the mug which heats my hands which are holding the mug. CONDUCTION 2. Heat flows from one place to another because the heated material itself moves. The warm winds blow and heat from the tropics ends up in Pennsylvania. CONVECTION 3. An object loses heat to the environment via electromagnetic waves. The wavelength of these waves is determined by the temperature of the object, with cooler objects giving off longer wavelengths. RADIATION
Match each of the basic types of energy with its definition.
1. The energy of moving things - Kinetic Energy 2. The energy an object has due to its position - Potential Energy 3. The energy released when atomic nuclei split or fuse - Nuclear 4. The energy of heat or temperature - Thermal 5. Energy transmitted via electromagnetic waves - Radiant 6. Energy stored in the bonds between atoms - Chemical 7. The energy of flowing electrons - Electrical
Kevin wants to use less fossil fuel by purchasing an electric vehicle. EV's are currently about 50% efficient. Gasoline engines are about 25% efficient. What is better for Kevin's wallet and for the environment?
25% overall efficient use of gasoline
A power plant converts 100 kJ of coal into 30 kJ of electrical energy. What is the efficiency?
30%
In 2019 the U.S. used 100.2 quads of energy out of which 67.5 quads were rejected energy. What is the US energy efficiency?
32%
There are a little more than 7.5 billion people on the planet today, but 2.5 billion people are using most of the energy. The UN projects that human population will stabilize around 10 billion people by the year 2100 - an addition of 2.5 billion more people. How much would energy use increase by if 10 billion people in 2100 are using the amount of energy 2.5 billion people are using today?
4x
`Your home converts 30 kJ of electrical energy into 15 kJ of useful energy (heat, electric) and 15 kJ of wasted energy. What is your home's efficiency?
50%
If Penn State's power generation is 70% efficient and campus efficiency (dorms, labs, lecture halls) is raised from 50% to 90%, what is the new process efficiency?
63%
Through a combination of fertility rate and decreased poverty levels, a population's energy use is growing exponentially 1% per year. How many years until the energy use doubles?
69.3 Years
The Penn State natural gas plant produces 7 MW of power.Part 2: What if Penn State could successfully reuse 1/3rd of the remaining rejected heat...what is the new process efficiency?
80%
Which has more kinetic energy?
A car moving at 120 mph across the Bonneville Salt Flats
Which has more potential energy?
A cubic mile of water (a lake) behind a 300 ft tall dam
Choose the answer that lists the correct sequence of steps in the process of turning fuel into electricity that is available in your home
A fuel is burned in a boiler. Water absorbs heat and boils into steam. High-pressure steam is directed through a turbine, causing it to spin. A turbine spins an electric generator, pushing electrons through wires. A step-up transformer reduces the current and raises the voltage. High-voltage power lines distribute the electric power to distant locations. A step-down transformer reduces the voltage and raises the current.
Which do you think is more efficient?
A jet engine that produces 70 units of work from 100 units of energy.
Chose the answer that lists the electromagnetic wave radiant energy forms in order, from longest wavelength to shortest, from lowest frequency to highest.
AM radio, microwave oven, heat from a person or pet, incandescent light bulb, UV - black light, dental X rays, gamma rays from a radioactive element
What did coal provide the developed world during the Industrial Revolution?
All of the above
Which has more nuclear energy?
An atomic bomb in a silo in North Dakota
Which has more chemical energy?
An oil tanker moored at a terminal
A ball of mass 2 kg is placed at position A at a height of 50 m from the ground. The initial velocity is 0 m/s. If the ball starts rolling down an inclined plane, what are the potential and kinetic energies at positions A, B, C and D in Joules assuming that the ball does not experience any frictional force (total mechanical energy does not change)? Please use 9.8 m/s2 for the gravitational constant when calculating potential energy. The heights of positions A, B, C, and D are listed below: A: 50 meters B: 25 meters C: 25 meters D: 0 meters Potential @ A Kinetic @ A Potential @ B Kinetic @ B Potential @ C Kinetic @ C Potential @ D Kinetic @ D What is the velocity of the ball in meters per second when it reaches point B or C (round to the nearest whole number)?
Answer 1: 980 Answer 2: 0 Answer 3: 490 Answer 4: 490 Answer 5: 490 Answer 6: 490 Answer 7: 0 Answer 8: 980 Answer 9: 22
What transformation occurs in a lawn mower?
Chemical to kinetic/mechanical
Kevin wants to use less fossil fuel by purchasing an electric vehicle. EV's are currently about 50% efficient. The power in Kevin's neighborhood comes from a coal-fired power plant. When Kevin plugs his EV in at night, what is powering his car?
Coal
The hot coffee heats the mug which heats my hands which are holding the mug. What method of heat transfer is it?
Conduction
Which of the following are units of energy? Check all that qualify.
Joule Calorie Kilowatt Hour BTU
Which series goes from least energetic to most?
Radio < infrared < ultraviolet < x-rays
What do you think "embedded" energy is?
The energy that goes into making something.
Which of the following are units of power? Check all that qualify.
Watt Horsepower
Kevin lives next to a power plant that burns coal. He wants to be more green, so he buys an electric car that he can plug into his home electricity. What is powering Kevin's car?
coal
