Energy Transformation – worksheet



Energy Transformation

8.3.13 Explain that energy cannot be created or destroyed but only changed from one form into another.

8.3.15 Identify different forms of energy that exist in nature.

We learned that Energy

• can be either Potential Energy (PE) or Kinetic Energy (KE)

• is measured in Joules (J)

• comes in 7 forms:

Mechanical (from moving objects)

Chemical (chemical bonds in a substance)

Thermal (heat energy)

Electromagnetic (travels through space as waves)

Sound (travels through air or other matter as waves)

Nuclear (from nuclear reactions)

Electrical (electricity)

We also learned that energy can neither be created or destroyed – only transformed. This is the Law of Conservation of Energy. The amount of energy in the universe is constant.

Apply what you have learned to answer the following questions:

1. A moving object has

A. kinetic energy

B. potential energy

C. both kinetic and potential energy

D. neither kind of energy

2. The energy stored inside a battery is

A. kinetic energy

B. potential energy

C. both kinetic and potential energy

D. neither kind of energy

3. In the picture below, in which position does the ball have the greatest potential energy?

[pic]

A. 1 B. 2 C. 3 D. 4

4. The purpose of a nuclear power plant is to transform nuclear energy into electricity. This is done in steps starting with a nuclear reaction which generates heat to produce steam. The steam in turn is used to turn a generator which finally produces electricity. Which answer best illustrates these energy transformation?

A. nuclear → mechanical → chemical → electrical

B. thermal → nuclear → mechanical → electrical

C. mechanical → thermal → nuclear →electrical

D. nuclear → thermal → mechanical → electrical

5. What energy transformation(s) take(s) place when you strike and light a match?

A. chemical to nuclear energy

B. mechanical to thermal energy

C. chemical to thermal and electromagnetic energy

D. electromagnetic to potential energy

6. PHOTOSYNTHESIS transforms electromagnetic energy from the Sun into

A. mechanical energy

B. thermal energy

C. chemical energy

D. electrical energy

7. Answering your cell phone transforms the chemical energy in its battery into

A. electromagnetic (light) energy

B. electrical energy

C. sound energy

D. all the above

8. Which of the pictures below illustrates the transformation of electrical to thermal energy? [pic]

Efficiency Formula

Efficiency is a measure of how much work or energy is conserved in a process. In many processes, work or energy is lost, for example as waste heat or vibration. The efficiency is the energy output, divided by the energy input, and expressed as a percentage. A perfect process would have an efficiency of 100%.

η = efficiency (Greek letter "eta")

Wout = the work or energy produced by a process. Units are Joules (J).

Win = the work or energy put in to a process. Units are Joules (J).

Efficiency Formula Example Questions:

1) A construction worker puts 20 J of energy in to one strike of his hammer on the head of a nail. The energy transferred to driving the nail in to the wood is 8.0 J. What is the efficiency of the construction worker's hammering?

Answer: The efficiency can be found using the formula:

[pic]

[pic]

η = 0.40 x 100%

η = 40%

The efficiency of the hammer strike was 40%. Vibrations and heating of the nail are two possible reasons for the energy loss.

2) A particular chemical process has an energy efficiency of only 3.00%. To complete this large-scale chemical process, 140,000 J of energy is input. What is the energy output of this process?

Answer: The energy output can be found by rearranging the formula for efficiency:

[pic]

[pic]

[pic]

Wout = (140,000 J)(0.03)

Wout = 42,000 J

The energy output of this chemical process is 42,000 J.

Answer the following questions and show your work.

A particular cell phone charger uses 4.83 joules per second when plugged into an outlet, but only 1.31 joules per second actually goes into the cell phone battery. The remaining joules are lost as heat. That’s why the battery feels warm after it has been charging for a while. How efficient is the charger?

A certain light bulb consumes 200J of electrical energy per second, but only emits 25J of light energy per second. Calculate the efficiency of this bulb.

A certain engine is filled with gasoline that contains chemical energy, and when the engine is started, it begins transforming that chemical energy into mechanical energy. Over the course of a few seconds, the engine transforms 7,000J of chemical energy, but 5,000J of that energy is ‘wasted’ in the form of thermal energy.

A certain solar panel is capable of absorbing 750J of light energy every second, and converting 150J of that energy into electrical energy

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download