The document summarizes key concepts about energy: 1) The human body gets its energy from food, which it converts from potential to chemical and kinetic energy to power movement and keep the body warm. Exercise and sleep help the body use and renew its stored energy. 2) Potential energy can be converted to other forms of energy, like food potential becoming kinetic energy for movement or thermal energy to produce heat. 3) Energy exists in many forms and can change from one to another through conversion systems, with some energy always lost as waste. The total energy entering and leaving a system remains the same according to the law of conservation of energy. 4) Electricity is generated through kinetic energy conversions using generators

1. Unit B Review
Science 24
October 28, 2015

2. Where does the body get it’s energy??
-The human body converts stored
(potential energy) in food into other
forms of energy
-Exercise speeds up the release of
chemical energy from food stored in the
muscles
-Sleep gives the body’s cells a chance to
clear waste products and renew stores of
energy

3. Using Energy to Do Work
Potential energy becomes useful
energy when:
-electric energy is converted into
light energy to light your room
-the stored energy in food is
converted to kinetic energy as you
walk out the door

4. Many Forms of Energy
-Solar energy
-Thermal energy
-Wind energy
-Geothermal energy

5. Energy Conversions
-energy that enters the system is
called input energy
-The system that changes energy
from one form to another is
called a converter
-The energy that leaves the
system is called output energy

7. Potential energy from food is
converted to kinetic energy for
muscles to move.
Potential energy from food is
converted to thermal energy
to keep you warm.

8. Thermal energy can be wasted!
-Think of when a person is
drilling into metal or another
hard material. What happens if
he drills for long periods of
time without stopping?

9. Conservation of Energy
The Law of Conservation of Energy
states that energy cannot be created
or destroyed. Energy can only be
changed from one form to another.
Input Energy = Output Energy

10. Energy Conversion Systems
If you touched a light bulb after it has been on for a
while, what would you feel?
A hood on a vehicle feels warm after it has been running
for a while. Why is that? A vehicle is built to get you from
one location to another, not to heat up the hood. So why
is this?
The gas in the tank of a vehicle is full of potential energy.
So why will only a third of it actually be used to move the
vehicle? Where does the rest of the energy go??
Input Energy = useful output energy + waste output
energy

11. Chapter
6:Electric Energy
at Home

12. In the early 1800’s, Michael
Faraday discovered that when you
pass a magnet through a coil of
wire, you generate electricity.
Using these observations, he made
the first generator.

13. A Generator
Input energy  converter 
output energy
Kinetic energy  generator 
electric energy

16. http://www.whatisnuclear.com/articles/nucreactor.html

17. Electric Energy and Power
Energy is the ability to do work.
Work is defined as force multiplied by
distance.
Work=force x distance

18. Force is measured in Newtons
1N•m= 1 joule
Power is the rate at which energy is
transferred. Energy= power x time
1 watt= 1 joule of energy per second

19. Kilowatt hours
Since the watt is a small amount of energy, the
utility companies use a unit of energy 1000x
greater.
One kilowatt hour (kW•h) is equal to 1000 watt
hours.
One appliance that uses 1000 watts in 1 hour uses
the same as a 1 watt light bulb that is on for 1000
hours.
Both use 1kW•h

20. Efficiency is a measure of how completely
input energy is converted to accomplish the
desired output energy.
Efficiency can be expressed as a percentage.
For example, if a motor is 80% efficient, 80
percent of the input energy is converted to do
the intended job. The other 20% is wasted.
Percent efficiency of an electric device:
useful energy output
total electric energy input X 100

21. Chapter 7: Energy for Life
-How plants capture energy from
the Sun
-How animals use their food for
energy
-How carbs, fats, and proteins are
used as a source of energy