understanding electricity… a hair raising experience

KATARIN MACLEODKatarin MacLeod

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Understanding Electricity…

A

Hair Raising Experience


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You walk across the rug, reach for the doorknob and..........ZAP!!! You get a shock.

Or, you come inside from the cold, pull off your hat and......BOING!!! All your hair stands on end. What is going on

here? And why does it only seem to happen in the winter?

The answer is:

STATIC ELECTRICITYhttp://www.sciencemadesimple.com/static.html


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Law of Conservation of Charges Neutral Objects and Charged Objects attract

and…

http://www.sciencemadesimple.com/static.html


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Balancing of Charges



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So how does this work?

http://www.photographersdirect.com/buyers/stockphoto.asp?imageid=65334


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• Van der Graff (VDG) generator is a machine that continually draws electrons off a large metal dome. The dome thus becomes strongly positively charged once the machine is turned on.

http://www.ap.stmarys.ca/demos/content/e_and_m/hair_raising/hair_raising.html


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Tesla and his Invention

http://www.tb3.com/tesla/


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http://bhs.broo.k12.wv.us/homepage/alumni/dstevick/tc.htm


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The Fine Details…

• The Tesla coil is a dynamic device. High voltage radio-frequency current is produced at the rate the spark-gap fires.

• 120 times a second would be typical. • Maximum arcs are produced in profusion immediately and

continue for as long as the coil is left running. • The sparks, poorly visible in strong light, appear quite strong

in subdued lighting conditions. • The arcs are purplish to whitish depending on whether they

are allowed to go to the open air or are drawn to a nearby grounded rod or wire.

• A ground wire held close produces very intense sparks.

http://bhs.broo.k12.wv.us/homepage/alumni/dstevick/tc.htm


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Safety of Tesla Coils…• Tesla coils are not harmless toys. One must constantly

be watchful of what is touched. • It is said that the r.f. current from the coil flows over the

surface of the skin, and is therefore not capable of killing.• However, it is also known that contacting a high-powered

discharge can cause burns and is extremely painful. The primary circuit of the coil is where the true danger lies; plenty of voltage and amperage here.

• An inadvertant touch of a fully charged primary capacitor, even with the coil *off*, can kill you.

• Primary voltages run up to 15,000 volts, but the discharger puts out anywhere from a quarter-million to a couple million volts depending on the input power.


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Static Electricity & Balloons

Question:

How can you make a balloon stick to the wall when only given the balloon?


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Answer

If you charge a balloon by rubbing it on your hair, it picks up extra electrons and has a negative charge.

Holding it near a neutral object will make the charges in that object move. If it is a conductor, many electrons move easily to the other side, as far from the balloon as possible.

If it is an insulator, the electrons in the atoms and molecules can only move very slightly to one side, away from the balloon.

In either case, there are more positive charges closer to the negative balloon. Opposites attract. The balloon sticks.



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Step 2: Using dryer sheets

What affect will occur if a charged balloon is then rubbed with a dryer sheet?

Will it still stick to the wall?


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The balloon will not stick to the wall because the dryer sheet removes the extra electrons added to the balloon…

Therefore, the balloon is now NEUTRAL and will not stick to the wall.

What charge must be on the dryer sheets?


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Direct Current Electric Circuits

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/dccircon.html#c1


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Series Circuits

In a series circuit, all elements are attached to make one complete path.

Here a battery is attached to three lights.

http://www.msnucleus.org/membership/html/k-6/as/technology/4/ast4_3a.html


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Real life Circuits vs. Schematic Drawings This drawing is a series circuit with a battery ( 3 cells

connected in series) and three lights (loads or resistors).

http://www.glenbrook.k12.il.us/gbssci/phys/Class/circuits/u9l4a.html


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DC Parallel CircuitsThe following is a parallel circuit. Notice the wires

are arranged such that the lights will be in parallel with each other.


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Real life Parallel Circuit vs. Schematic Diagram

http://www.glenbrook.k12.il.us/gbssci/phys/Class/circuits/u9l4a.html


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Science Fairs & Science Olympics• There are stages to Science Fairs:

SchoolRegionalProvincialNational International

• All grades can participate and projects are grouped depending on grade and topic

• Money and scholarships are given out as students progress through the various stages of fairs

http://www.physics.uwo.ca/sfair/sflinks.htm


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More on Science Fairs…For examples:

http://school.discovery.com/sciencefaircentral/

(separate science fair guides for students, teachers and parents)

http://www.scifair.org/ (“ultimate science fair resource – science project help & ideas)

http://www.virtualsciencefair.com/ (Canada wide virtual science fair for K-12)


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Science Olympics

• The general idea is that students pursue excellence through science and/or competition.

• These can be held at a school or regional level.

• Best site:

http://www.physics.uwo.ca/olympics


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Welcome to theFirst Annual

Secondary Science Olympics


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First Event…

The Solo-Electromagnet Competition

• In pairs, work to build an electromagnet.

• Materials: 1m of wire, 1 nail, 1 9V battery, and paperclips


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Procedure• Wrap the wire around the nail

• Attach the ends of the wire to the terminals of the battery

• Try to pick up as many paperclips with the electromagnet as possible

• The maximum number of paperclips is your score for this event.


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Second Event…

The Duo-Boat Float

• In pairs, you will build a boat from Aluminum foil and test for buoyancy

• Materials: 1 15cm x 15cm piece of Aluminum foil, container of water, & washers.


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Procedure• Create a boat from the Aluminum foil

• Test to see if it floats

• Add pennies, washers or nails to your boat until it sinks into the water

• The number of items added to your boat is your score for this event.


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The Third and Final Event…

The Quad-Straw Free Standing Tower

• In groups of 2, you will build the tallest possible free standing tower.

• Materials: 10 straws, 1 sheet of paper, 20cm of tape


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Procedure

• From the materials given, construct the tallest possible tower

• When all towers are complete, the tallest in the class will receive 100 points, the second tallest will receive 50 points and the third tallest will receive 25 points.


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Calculating Time…

Solo-Electromagnet: # of paperclips

Duo-Boat Float: # of pennies held

Quad Straw Free Standing Tower: points

Final Score: ____________

Congratulations!


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Thank you for Participating

Have a Great DayPrizes will be awarded

On Wednesday!

understanding electricity… a hair raising experience

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