THE ENERGY CONNECTION

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```					Science Focus 9                             Electricity                                     Topic 4

THE ENERGY CONNECTION

   It’s Ethan’s turn to help out in the kitchen. He places a water filled pot on the stove and
turns on the element. It’s not long before the water is hot. Ethan will use the hot water to
prepare vegetable soup.

   His mind is on food preparation – it’s not on the energy transformation underneath the
pot. That’s where electricity is transformed into thermal energy.

* Turn to page 293 of your textbook and read the top paragraph. Refer to the activity on page
293. Also read the opening paragraph, then carry out steps 1 and 2 of “Procedure”.

QUESTION 1:
Answer question 2 of “What Did You Find Out?”.

ELECTRICITY AND HEAT

   Can you think of a device that converts thermal energy to electrical energy? Many home
furnaces have a pilot light that has to stay on all the time. It lights the main burner. A
safety device turns off the gas supply valve if the pilot light goes out.

   A THERMOCOUPLE is the heart of the safety device. The thermocouple produces
electricity only with the heat of the pilot light. An interruption in the flow of electricity
signals the safety device to close the gas supply valve.

* Turn to pages 294 and 295 of your textbook and read “Electricity and Heat” to find out more

QUESTION 2:
Does any combination of metals work for a thermocouple?

QUESTION 3:
How is the thermopile in a thermo – electric generator built?

ELECTRICITY AND MOTION

   You probably listen to music on a MP3 player or an iPod. But some people still play
vinyl records on a turntable. Many DJs like the turntable for its ability to add “scratch”
sounds to music. The needle of the turntable normally follows along the squiggly
grooves in a record spinning under it.

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Science Focus 9                            Electricity                                    Topic 4

   A DJ may make the needle scratch across the grooves for a special effect. The vibrating
movement of the needle is converted into electrical energy, which is amplified to run the
speakers and produce the sound.

   Maybe you can think of a device that directly converts electricity to motion or vice versa?
No? The next reading will deal with such devices.

* Turn to pages 295 and 296 of your textbook and read “Electricity to Motion” and “Motion to
Electricity”.

* Read about the piezoelectric effect on pages 295 and 296 of the textbook, including the
introductory paragraph of “Find Out Activity: Flashing Rocks”.

ELECTRICITY AND LIGHT

   The International Space Station is completely powered by large panels of solar cells.
These panels convert light energy to electrical energy.

   You are probably familiar with more down – to – earth examples of light to electricity
transformations. Just think of             solar – powered calculators, watches, and

* Find out more about transformations of light and electricity in the reading on page 297 of the
textbook.

QUESTION 4:
What are the advantages of an LED over a conventional light bulb?

QUESTION 5:
How does a solar cell produce electricity from light?

QUESTION 6:
To test your understanding of the concepts in this lesson, answer questions 2 to 4 of “Topic 4
Review” on page 299 of your textbook.

KEY TERM:
   THERMOCOUPLE: a loop of two wires made of different types of metals that
converts heat to energy

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