Galvanometers are coils of wire connected to a battery. When current flows through the wire, it creates a magnetic field. Since the wire is bundled up, it multiplies this electromagnetic effect to create a simple electromagnet that you can detect with your compass.
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Here’s what you need to do:


Materials:


  • magnet wire
  • sand paper
  • scissors
  • compass
  • AA battery case
  • 2 AA batteries
  • 2 alligator clip wires


Download Student Worksheet & Exercises


1. Remove the insulation from about an inch of each end of the wire. (Use sandpaper if you’re using magnet wire.)


2. Wrap the wire at least 30-50 times around your fingers, making sure your coil is large enough to slide the compass through.


3. Connect one end of the wire to the battery case wire.


4. While looking at the compass, repeatedly tap the other end of the wire to the battery. You should see the compass react to the tapping.


5. Switch the wires from one terminal of the battery to the other. Now tap again. Do you see a difference in the way the compass moves?


You just made a simple galvanometer. “Oh boy, that’s great! Hey Bob, take a look! I just made a….a what?!?” I thought you might ask that question. A galvanometer is a device that is used to find and measure electric current. “But, it made a compass needle move…isn’t that a magnetic field, not electricity?” Ah, yes, but hold on a minute. What is electric current…moving electrons. What do moving electrons create…a magnetic field! By the galvanometer detecting a change in the magnetic field, it is actually measuring electrical current! So, now that you’ve made one let’s use it!


More experiments with your galvanometer

You will need:


  • Your handy galvanometer
  • The strongest magnet you own
  • Another 2 feet or more of wire
  • Toilet paper or paper towel tube

1. Take your new piece of wire and remove about an inch of insulation from both ends of the wire.


2. Wrap this wire tightly and carefully around the end of the paper towel tube. Do as many wraps as you can while still leaving about 4 inches of wire on both sides of the coil. You may want to put a piece of tape on the coil to keep it from unwinding. Pull the coil from the paper towel tube, keeping the coil tightly wrapped.


3. Hook up your new coil with your galvanometer. One wire of the coil should be connected to one wire of the galvanometer and the other wire should be connected to the other end of the galvanometer.


4. Now move your magnet in and out of the the coil. Can you see the compass move? Does a stronger or weaker magnet make the compass move more? Does it matter how fast you move the magnet in and out of the coil?


Taa Daa!!! Ladies and gentlemen you just made electricity!!!!! You also just recreated one of the most important scientific discoveries of all time. One story about this discovery, goes like this:


A science teacher doing a demonstration for his students (can you see why I like this story) noticed that as he moved a magnet, he caused one of his instruments to register the flow of electricity. He experimented a bit further with this and noticed that a moving magnetic field can actually create electrical current. Thus tying the magnetism and the electricity together. Before that, they were seen as two completely different phenomena!


Now we know, that you can’t have an electric field without a magnetic field. You also cannot have a moving magnetic field, without causing electricity in objects that electrons can move in (like wires). Moving electrons create a magnetic field and moving magnetic fields can create electric currents.


“So, if I just made electricity, can I power a light bulb by moving a magnet around?” Yes, if you moved that magnet back and forth fast enough you could power a light bulb. However, by fast enough, I mean like 1000 times a second or more! If you had a stronger magnet, or many more coils in your wire, then you could make a greater amount of electricity each time you moved the magnet through the wire.


Believe it or not, most of the electricity you use comes from moving magnets around coils of wire! Electrical power plants either spin HUGE coils of wire around very powerful magnets or they spin very powerful magnets around HUGE coils of wire. The electricity to power your computer, your lights, your air conditioning, your radio or whatever, comes from spinning magnets or wires!


“But what about all those nuclear and coal power plants I hear about all the time?” Good question. Do you know what that nuclear and coal stuff does? It gets really hot. When it gets really hot, it boils water. When it boils water, it makes steam and do you know what the steam does? It causes giant wheels to turn. Guess what’s on those giant wheels. That’s right, a huge coil of wire or very powerful magnets! Coal and nuclear energy basically do little more than boil water. With the exception of solar energy almost all electrical production comes from something huge spinning really fast!


Exercises


  1. Why didn’t the coil of wire work when it wasn’t hooked up to a battery? What does the battery do to the coil of wire?
  2. How does a moving magnet make electricity?
  3. What makes the compass needle deflect in the second coil?
  4. Does a stronger or weaker magnet make the compass move more?
  5. Does it matter how fast you move the magnet in and out of the coil?

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Comments

One Response to “Galvanometers”

  1. gulnora12 says:

    What if you have iron ore and smelt it so it is 100% iron and you shape it into a torch and you put a light bulb onto it, will it be on as long as you shake it?