1. I use floating magnets to demonstrate the forces (attraction = opposite poles & repulsion = like poles) of magnetism. I take two of the same magnets and put them on the top of the overhead projector to cast a shadow on the screen to show what happens to the magnetic field as the distance increases and decreases. I pass the magnets around the class so that the students can experience the magnetic forces of attraction and repulsion.
2. We also make magnets by magnetic induction by laying a screwdriver next to a magnet in order to align the magnetic domains, and stroking the screwdriver in one direction witha permanent magnet. Then we randomize the magnetic domains by heating and banging the temporary magnets. Students are able to see how the magnet loses its magnetism when we randomize the domains.
3. Another temporary magnet that we make is an electromagnet. The students are made aware that a current carrying wire has a magnetic field that surrounds it. (We can show that by using a compass to detect the magnetic field.) We use a source of voltage, like a battery, a wire, and an iron nail. We are able to pick up paperclips and my car keys, and then drop them off in a different area when we open the circuit. In order to increase the strength of the magnetic field we put more coils around the nail, we add more nails, and we increase the voltage in order to increase the current.
Students absolutely love seeing how these scientific concepts can be applied. This makes something that is abstract, concrete and helps them to understand, and enjoy coming to class.
Wednesday, December 17, 2008
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.
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.
Static Electricity
So here are some fun experiments to do with your classes in reference to static electricity:
1. Rub a balloon on a student's head. Ask the students why the student's hair was attracted to the balloon. (Possible answer: the balloon gained electrons & has a negative charge, the hair lost electrons & has a positive charge & opposite charges attract each other.) Friction (the force that opposes motion) due to rubbing removed the electrons.
2. Use the Van de Graff Generator. Explain to the students that the rubber band has friction as it moves and the electrons build up on the metal ball (the build up of electrons without further movement = Static Electricity) When the electrons jump off the metal ball (Electric Discharge) you can hear the sound, feel the shock, and see the blue light. (This is lightening on a smaller scale). Students can experience this first hand & have a great time.
3. Have a student put her hands on the metal ball of the Van de Graff generator. Students will notice her hair standing up. Ask the students why that would happen. (Possible answer: electrons build up on the student giving the student a negative charge. The individual hairs repel each other because they are like charges & like charges repel each other.)
4. Students can also view like charges repelling each other by using an electroscope to detect electric charge. Charge a rubber rod by rubbing it on rabbit's fur. It will gain electrons. Touch the rod to the top of the electroscope. The electrons will travel down the metal ball to the metal leaves, which will repel each other. Students will be able to see that like charges repel each other. (This can be done with a positively charged glass rod. However, the electrons will move off the metal ball giving the metal leaves a positive charge.)
5. Students will be able to relate to static electricity because they have experienced a shock when walking across a room and touching a door handle, taking socks with static cling out of the drier, or numerous other experiences.
This topic is so much FUN!!!!!
1. Rub a balloon on a student's head. Ask the students why the student's hair was attracted to the balloon. (Possible answer: the balloon gained electrons & has a negative charge, the hair lost electrons & has a positive charge & opposite charges attract each other.) Friction (the force that opposes motion) due to rubbing removed the electrons.
2. Use the Van de Graff Generator. Explain to the students that the rubber band has friction as it moves and the electrons build up on the metal ball (the build up of electrons without further movement = Static Electricity) When the electrons jump off the metal ball (Electric Discharge) you can hear the sound, feel the shock, and see the blue light. (This is lightening on a smaller scale). Students can experience this first hand & have a great time.
3. Have a student put her hands on the metal ball of the Van de Graff generator. Students will notice her hair standing up. Ask the students why that would happen. (Possible answer: electrons build up on the student giving the student a negative charge. The individual hairs repel each other because they are like charges & like charges repel each other.)
4. Students can also view like charges repelling each other by using an electroscope to detect electric charge. Charge a rubber rod by rubbing it on rabbit's fur. It will gain electrons. Touch the rod to the top of the electroscope. The electrons will travel down the metal ball to the metal leaves, which will repel each other. Students will be able to see that like charges repel each other. (This can be done with a positively charged glass rod. However, the electrons will move off the metal ball giving the metal leaves a positive charge.)
5. Students will be able to relate to static electricity because they have experienced a shock when walking across a room and touching a door handle, taking socks with static cling out of the drier, or numerous other experiences.
This topic is so much FUN!!!!!
Static Electricity
One of the best topics that we cover in Science 8-R is the topic of Electricity. In order to have the students understand the topic we first have to cover the parts of the atom with emphasis on what happens when electrons are lost and gained. It can be hard for students to remember how an object becomes positively charged so I tell them this joke (I didn't make it up, but it's a good one.) Two atoms walk into a bar, the first one says, "OOh I think I just lost an Electron. The second one says, "Are you sure?" and the first one replies, "Yes, I'm POSTITIVE." So the students recognize that anytime an object loses electrons that it will have a positive charge.
Another joke is in reference to the neutron (again I didn't make it up). A neutron orders a drink and then says to the bartender, "Hey, how much do I owe you?" and the bartender replies, "For you, NO CHARGE."
Anyone else have some good science jokes?
Another joke is in reference to the neutron (again I didn't make it up). A neutron orders a drink and then says to the bartender, "Hey, how much do I owe you?" and the bartender replies, "For you, NO CHARGE."
Anyone else have some good science jokes?
Tuesday, December 16, 2008
This is Nothing New(ton)
My classmates and I put together a video on Newton's First Law of Motion. We had a great time filming it. However, it has been an agony and ecstacy to put the whole package together. We have found that technology can be very difficult to manipulate at times and we definitely experienced some frustration when dealing with some of the web-sites. Just one space off, or one tiny period off can be the difference between completing a project in a timely manner, or spending an inordinate amount of time troubleshooting in order to get back on track. But, once everything falls into place... wow, the relief and happiness of knowing that you can move on to the next task at hand.
Subscribe to:
Posts (Atom)