Drawing On Science For Kids
neutrons, protons and electrons. Unlike the first two, electrons weigh practically nothing and can freely leave the atom and move around. And this is a good thing. You see, electricity is caused by electrons leaving their atoms and moving around.
The problem is controlling the electrons as they travel. This is done by something called a conductor. Metals are excellent conductors of electrons because metal atoms give up their electrons very easily. The wiring in your house is made of copper, a metal which is a very good conductor of electrons. But then, there's another problem. If you touch the wire while the electrons are moving through it, you will get a shock. This is not good, so to prevent a shock the wire has to be insulated. An insulator such as rubber, plastic, or wood is a non-conductor of electricity, which means that electrons can't flow through it. Electric wires are covered with an insulator so that we can't be shocked by the electric current traveling through the wire. This is called current electricity because the movement of electrons through a conductor is called an electric current. The path taken by the electrons from their source through the wire and back to the source is called an electric circuit.
Then, there's frictional or static electricity. Static means "at rest." We've all rubbed a balloon on our heads and stuck it to a wall. The electricity is stored on the balloon's surface until it's brought close to another object. Then we hear a kind of "cracking" sound due to positive electrons being attracted to negative electrons.
When an electric current passes through a wire, a magnetic field is produced around that wire. On the other hand, if you pass a magnet over a metal wire, you create an electric current, because the electrons will begin to move. Moving electrons have energy so they can perform some sort of work. A microwave oven, toaster, refrigerator, TV, and your iPod all depend on an electrical current to make them work.
A battery is a common source of electricity. It is made of special chemicals which, when they come in contact with each other, produce an electric current. You can control an electric current by placing a switch between the source and the object, using the electricity. When the switch is open (off), no current is passing through the wire.When the switch is closed (on), an electric current is allowed to pass through the wire.
A magnet is able to attract metals such as iron, steel, and nickel.
Lodestone (an ore of iron) is a natural magnet. An artificial magnet can be made by rubbing a piece of steel with a lodestone or passing an electric current through it. The bar or U-shaped magnet you buy in a store is an artificial magnet. If you suspend a bar magnet on a string it will spin around until it comes to rest in a north-south position. The end pointing north is called the north pole of the magnet and the end pointing south is the south pole. If a north pole of one magnet is placed close to a south pole of another magnet, they will attract each other. If two similar poles are placed near each other, they will repel each other.
An electric motor is simply a circular coil of bare wire held by its straight ends, resting on a support which conducts electricity. Half of the support ends are bare wire, while the other half are insulated. The coil is placed next to a magnet. When the bare wire rolls onto the supports, an electric current passes through the coil and the wire is attracted to the magnet. When the insulated half rolls onto the support, no electricity passes through the coil and the wire is not attracted to the magnet. This "on again, off again" of an electric current causes the circular coil of wire to spin. If this coil of wire is attached to a shaft with fan blades, then we have a spinning fan.
You can demonstrate the relationship between electricity and a magnet with an electromagnet. When a current of electrons is moving through a wire, a magnetic field is produced around the wire. An electromagnet consists of a coil of insulated wire wound around a piece of iron. The wire is then connected to a source of electricity.
To make your own electromagnet (see diagram) you'll need: insulated bell wire; a three-inch nail (called a 10- penny nail); a 12-volt lantern battery; a compass; a switch such as a knife switch; and some paper clips. 1. Tightly wind the insulated bell wire around the nail about 25-35 times, leaving about six inches of wire free at each end. 2. Peel off some insulation from the ends of each wire end. 3. Connect one end of the wire to a knife switch and connect the switch to one pole of the battery. 4. Connect the other wire end to the other battery pole. 5. Turn the switch on and bring the nail close to a pile of paper clips. What do you observe? What happens when you open the switch (turn it off)? How many clips can your magnet pick up? How can you make the magnet more powerful?
With the switch on, hold one end of the nail near the compass needle. Observe what happens. Then hold the other end of the nail near the compass needle.
How does the needle move in each case? Now reverse the wire connections to the battery and repeat the experiment with the compass.
Does an electromagnet have poles?
Can the poles be reversed?
Questions/comments? E-mail Steve: Drawingonscience@ aol.com