Current Electricity

Electric Current refers to the flow of electrons through a material. Conductors such as metals (copper, silver) are good materials for conductions because they don't hold on to their electrons as tightly as insulators.

I do a few demonstrations with my class to help them under stand some of the abstract ideas behind Ohms Law (Voltage = Current X Resistance or V = I X R)

1. I speak to my students in reference to the beach and ask them what we call the flow of water. (They usually know that it's called a current.) Hence, the flow of electrons = electric current

2. I have my students pile into the middle isle of the room. They represent atoms of copper. I am an electron that tries to move through them. Since they are crowded in the center of the isle, I bump into them. They resist my flow. Therefore, resistance is the opposition to the flow of electrons. So we will never have the flow of electrons without the resistance to the flow of the electrons.

3. I then hold up a wire from the overhead projector, which is unplugged and ask my students if there is an electric current running through the wire. They know the answer is "no". I ask them what I need to do to get the electrons flowing, and they tell me to plug it in. I ask them what type of charge electrons have. They know negative. I ask them what type of charge will attract a negative charge, and they tell me positive. Therefore, we require an electric potential difference, or a source of voltage in order to create an electric current.

4. I show the students a battery. They are able to point out the positive and negative terminals and the students are able to relate to the Electric Potential Difference. Hence, the battery is a source of voltage.

5. We analyze the battery and students are able to conclude that the positive terminal is created by a chemical reaction that removes electrons, and the negative terminal is created by chemical reaction that adds electrons to the terminal.