Download COE Unit Test Study Guide Define the following words: • Energy

COE Unit Test Study Guide
Define the following words:

Energy –the ability to do work

Simple machine –a device that reduces the force applied

Mechanical energy –potential and kinetic energy combined

Law of conservation of energy –Energy cannot be created or destroyed. Energy can only
be transformed or transferred from one form/object to another. The total amount never
changes.

Generator –transforms mechanical energy into electrical energy

Motor –transforms electrical energy into mechanical energy

Magnetic field -area around a magnet that applies a force without actually touching the
object

Fixed pulley –a pulley that only changes the direction of the applied force

Efficiency -a measure of how much of the work (or energy) that is put into a machine
results in useful work (or energy)

Insulator – a material that does not allow thermal energy to pass through it easily

Conductor – a material that does allow thermal energy to pass through it easily

Radiation -the transfer of energy through space without particles moving or colliding to
transfer the energy
Conduction – the transfer of heat through the contact of materials

Convection –the transfer of heat through currents of liquids or gases
Answer the following questions:
1. Can the efficiency of a machine be over 100%? Explain. No machine can transfer all of
the energy that is applied to it to useful work. In other words machines are never 100%
efficient.
2. How do you improve the efficiency of the following machines:
a. Lever – change the design of the machine to increase the distance over which the
effort force acts or reduce the friction.
b. Inclined plane – Reduce the friction or change the design of the machine to
increase the distance over which the effort force acts
c. Pulley - Reduce the friction or change the design of the machine to increase the
distance over which the effort force acts
3. How do you know that work is being done on an object? You exert a force and the object
moves a distance
4. Give an example of work being done. Answers will vary, but make sure they meet the
criteria of the scientific definition of work
5. Give an example of an insulator. Answers will vary
6. Give an example of a conductor. Answers will vary
7. Give an example of radiation. The sun, standing next to a fire
8. Give an example of conduction. Spoon in hot soup; pan touching the eye of a stove
9. Give an example of convection. Global winds; ocean currents; boiling water
10. How does heat transfer? Heat always moves from warmer objects to cooler objects
11. How does the electric motor work? Electricity makes a coil of wire act like a magnet
which is repelled by a permanent magnet.
12. What happens when a switch closes in an electric circuit? The circuit is complete, and
electricity can flow.
13. What occurs when a nail wrapped in a wire is attached to an electric circuit? The nail
becomes an electromagnet
14.
What problems could cause the light bulb NOT to light up? The circuit
is incomplete; the bulb is burned out; the battery is dead
15. Complete energy conversions for the following items/situations:
a. Plants light energy to chemical energy
b. Door bell electrical energy to sound energy
c. Electric fan electrical energy to heat energy, sound energy, and mechanical energy
d. Hair dryer electrical energy to heat energy and sound energy
e. Moving leg chemical energy to mechanical energy
f. Stretched rubber band potential energy to kinetic energy
g. Wood at a campfire chemical energy to thermal energy
16. Why would an electric company build a dam in a river? They might want to convert the
potential energy of the water into electrical energy for their customers.
17. Using the picture, answer the following questions:
a. At what point would you find the most potential energy? Point A
b. At what point would you find the most kinetic energy? Point D
c. At what point would you find both potential and kinetic energy? Point C
18. Give an example of potential energy. Answers will vary
19. Give an example of kinetic energy. Answers will vary