Electrical Circuits: You can Do It! (1986)

motion we all enjoy things that [Music] move making things happen by throwing a switch is fun creating light can be very useful many things that move or light up or get warm do so because of electricity what is electricity well remember that all matter is made up of tiny atoms hovering around the center of each at are clouds of constantly moving electrons it's the motion of these electrons that creates electricity of course you can't see moving electrons but you can detect their presence try this little experiment let's look at that again when you scuff your feet across the carpet electrons move from the carpet onto your body this buildup of electrons is called static electricity when you touch the steel case other electrons jump back from your body all at once you have lost your static electricity sometimes electrons don't jump from place to place but they can pull things like this fur towards this balloon during a thunderstorm you can see the results of static electricity electrons gather within the swirling clouds suddenly they jump in less than a second trillions of electrons move from the cloud to Earth although spectacular this form of static electricity isn't very practical there's another kind of electricity called current electricity it flows smoothly rather than jumping current electricity Powers this train we can't see electrons jumping from place to place so where is the electricity in this case electrons flow from the red switch boox through a wire into one of the tracks from there they move through one of the train wheels and into the motor but the electrons don't stop there they continue into a second track and back to the red switch boox we call this complete Loop of flowing electrons an electrical circuit as long as the circuit is complete the electrons flow and the train runs but suppose we stop the train and try an experiment disconnecting part of the circuit should have an effect since the flow of electrons is broken all motion stops completing the circuit gets things moving again devices that allow us to easily break and reconnect circuits are called switches closing this switch allows electrons to flow through these wires and into the vibrating motor of the barrel loader or try this with your refrigerator light here's a type of switch that will test your steadiness if the copper wire touches any of the loops the circuit is completed and the light tells you that your nerves aren't what they should be but why are most wires that carry electricity made out of copper and covered with plastic to find out we can try this simple Penny toss game the copper strips on this board make a circuit that can only be completed when a penny touches two strips at once but what happens if we substitute a plastic disc for the copper disc the plastic doesn't seem to complete the circuit perhaps the electrons in the plastic don't flow as well as those in the copper penny if we could compare the flow of electrons through plastic and copper we'd see that plastic atoms resist or slow down their electrons for this reason we call plastic a poor conductor of electricity which is also why we use plastic as an insulator copper on the other hand has a lower resistance and lets electrons flow more easily so copper is called a good conductor we can see that a conductor's resistance depends on the substance it's made of but resistance also depends on a conductor's length these two wires were cut from the same spool but one is short and the other is very long the light with a long wire glows dimly while the light with the short wire is quite a bit brighter the extra amount of electrons in the longer wire seems to slow down the flow of electricity making the light dimmer besides its substance and length there's something else that affects a conductor's resistance can you see the difference between these two copper cables would electrons flow more easily through the big one or the small one to help us think about it imagine that we are looking at the end of a highway it's rush hour but the traffic is moving quite freely now imagine parts of the highway closed for construction the same number of cars must pass through fewer Lanes traffic slows down now imagine that the cars are electrons the thick conductor passes electrons more easily than the thinner one we can say that the thinner one has a higher resistance conductors with a high resistance usually give off some form of energy such as light the thin filament in this vacuum light bulb glows as more and more electricity is pushed through through it the lack of air prevents it from burning up to launch a model rocket however we need a thin wire that heats up very quickly when we place the wire inside this rocket propellant we can have a liftoff at a safe distance we've seen three things that can change a conductor's resistance one is the substance it's made of the second is its length a longer conductor has a higher resistance the third is its thickness a thin conductor has a higher resistance than a thicker one but what makes the electrons flow in the first place this train gets its power from an outlet on the wall the outlet is part of another circuit that connects to a power line outside the house this power line connects with other lines over many miles all the way to the original power source there are many sources of electrical power but in this case the flow of millions of gallons of water creates our electricity some of this rushing water flows under this building called a hydro generating plant inside Giant turning machines called generators change the motion of the water into flowing electrons this generator in Dixon Illinois has been creating electricity for over 60 years without burning fuel of any kind you may have a smaller generator on your bicycle it turns the movement of a wheel into electricity for your head and tail [Music] lights but many things that move rely on a different type of power source batteries can be used to store power from an electrical circuit these batteries are being charged with electrons which will later be released to power these robot delivery cards here's a battery that runs on apple juice a chemical reaction between the fluids in these apples and the metal probes moves enough electrons to power a digital clock this photoelectric cell is another source of current when light hits the cell electrons start moving through the circuit take away the light and the current stops sunlight hitting these cells charges a battery for a train signal many miles from the nearest [Music] outlet astronauts in space don't have power lines either so scientists are developing some very sophisticated ways of generating electricity thousands of photo elect cells are built into this giant panel as the panel unfolds toward the sun billions of electrons start flowing through the spacecraft circuits perhaps technology such as this will someday lead to new sources of electricity for all of us on the planet 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