Electricity Week 2. Generator

coil_magnet

Nearly all of the electric power on Earth is generated at power stations by electromechanical generators.

An electric generator* is a machine that converts mechanical energy to electricity.
*Note: a generator itself does not produce electric power.

The primary components of all generators are magnets and wire coils. Every generator works on the basis of electromagnetic phenomena associated with the relationships between electricity and magnetism. An electric current produces a magnetic field, and vice versa.

1820 – Danish scientist Hans Christian Ørsted (pronounced “ersted”) discovered that electric currents create magnetic fields.
1824 – British scientist William Sturgeon invented the electromagnet.

An observation of these cause-and-effect relationships helps us to understand how electromechanical generators work. The best way to introduce children to the idea of electromagnetic phenomena is to do a series of experiments. The goal is to recreate the path of discovery scientists took while exploring electromagnetism in the first half of the 19th century.

Let’s try making our own electromagnet!

ELECTROMAGNET PROJECT

Materials needed:

– large iron nail
– thin coated (insulated) copper wire
– dry cell battery
– electrical tape
– paper clips (or other magnetic items)
– wire strippers
Image source: www.youtube.com/watch?v=PwVuLK0Q-po

Image source: www.youtube.com/watch?v=PwVuLK0Q-po

Steps:

1) Wrap the wire around the nail, leaving at least 10 inches of wire at the end. (Note: don’t overlap the wire when you wrap it)
2) Once the nail is wrapped, cut the wire, leaving about 8 to 10 inches on that end too.
3) Peel the insulation off both ends of the copper wire.
4) Attach one end of the wire to the positive terminal, and the other end to the negative terminal of the battery. Tape both ends to the battery terminals to keep them in place.
5) Test your electromagnet on paper clips or other magnetic items.

Discussion points:

1) The electric current running through the wire generates a magnetic field. We can observe this by the effect it has on the paper clips.
2) However, the magnetic field created by the electromagnet is temporary. It exists only as long as there is electricity running through the wire. Try disconnecting one end of the wire from the battery to see how the electromagnet loses its magnetism.

Beginning in 1830, US scientist Joseph Henry systematically improved and popularized the electromagnet.

You too can make your electromagnet more efficient by:

1) Increasing the number of wire turns
2) Using a battery that can provide a higher current
3) Choosing a bigger nail

Warning! Be careful, too much current can be dangerous because of the heat generated.

SIMPLE ELECTRIC GENERATOR PROJECT

After the invention of electromagnet, English scientist Michael Faraday theorized that if it was possible to make a non-magnetic object (the iron nail in our case) magnetized by adding electricity, then it should also be possible to generate electricity using magnets.

Let’s discover this possibility for ourselves by making our own simple generator similar to the one invented by Faraday back in 1831.

Materials needed:

– coated copper (or other magnetic wire) 40-60 feet, or 15 m long
– strong bar magnet
– hollow tube (paper towel cardboard cylinder)
– voltmeter or multimeter
– tape
– wire strippers
Image credit: sciencewithkids.com

Image credit: sciencewithkids.com

Steps:

1) Leaving approximately 6″ of wire slack, start wrapping the wire around the tube. Keep wrapping until about 6″ of wire remains.
2) Secure its ends using tape.
3) Peel the insulation off both ends of the wire, and attach them to a multimeter or voltmeter.
4) Set the voltmeter (or multimeter) to test for DC voltage, and make sure it’s set for the lower voltage unit.
5) Place the magnet inside the tube and move it quickly back and forth. If it helps, tape the magnet to a rod.
6) As you move the magnet, observe the voltmeter voltage readings.
7) Set the voltmeter to test for DC current and repeat the observation while moving the magnet quickly back and forth inside the tube.

Discussion points:

1) The magnet affects electrons inside the wire. Its magnetic field makes them move by pushing and pulling them. If the magnet inside the tube does not move, neither do the electrons inside the coil.
2) When you move the magnet back and forth or spin it, the magnetic field near the wire also changes. The changing magnetic field produces an electric current by making electrons in the wire move. This phenomenon is called Faraday’s law of electromagnetic induction. The majority of electric generators operate on the basis of Faraday’s law.

We can build a more efficient generator by:

1) Choosing a stronger rare-earth magnet
2) Choosing a slightly thicker gauge magnet wire
3) Finding a way to move the magnet quicker*

*If we had a powerful mechanical force moving the magnet, then that would generate more electricity. For example, we could attach the magnet to a group of gears and rotate it at a higher speed.

To generate electricity for big cities, powerful jets of steam are used to rotate shafts of gigantic generators comprised of complex arrangements of magnets and coiled wires. Where do they get the steam? The steam comes from thermal power stations. Burning various types of fuel, such as coal or gas, is used to boil a vast amount of water. At hydro power stations the force of falling water rotates generator shafts.

VIRTUAL CHILD-FRIENDLY ELECTRIC GENERATORS

Crayon Box How to Make Electricity Science View

Labs 2 and 3, of the How to Make Electricity app, allow kids to build simple interactive prototypes of hydroelectric and thermal power plants. Children are offered three types of coils to choose from. The goal is to figure out the most efficient way to rotate the magnet. The magnetic field and the effect it has on electrons are visible in the science view mode. Implementing visual aids does a tremendous job helping further a child’s understanding of the nature of electromagnetic phenomena explained by Faraday’s law.

Crayon Box How to Make Electricity - Generator

AppStore

Download the ‘How to Make Electricity‘ app from the App Store.
Download free lite version of the ‘How to Make Electricity’ app.

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