1. GALVANOMETERS, MAGNETIC FORCES, AND BATTERIES SECTION 5.3 AND 5.4

2. WHAT IS A GALVANOMETER? HTTPS://WWW.YOUTUBE.COM/WATCH?V=XMQBZNJO_WS HTTPS://WWW.YOUTUBE.COM/WATCH?V=XMQBZNJO_WS A galvanometer is used to detect and measure small amounts of electric current in circuits. It does this by responding to magnetic forces that are generated by an electric current. ( Remind you of an electromagnet? It should!)

3. THINK ABOUT IT: How is a galvanometer like an electromagnet? What common characteristics do you notice? What do you think happens when you wind more copper wire around the compass and pass a current through it? Why do you think it is a good idea to include a switch when constructing a galvanometer?

4. MAGNETIC FORCE Magnetic force is strongest near the poles. The forces become weaker as you move away from the poles and is weakest near the middle of the magnet. http://www.kjmagnetics.com/blog.asp?p=magneti c-forces (magnetic forces video) http://www.kjmagnetics.com/blog.asp?p=magneti c-forces

5. MAGNETIC FIELD One big difference between electricity and magnetism is that we can point to an electron and say “Here is a particle with a negative charge.” We cannot point to any particle of a magnet and say “Here is a north pole particle. “ You can cut a magnet into smaller and smaller pieces and it will always have a north pole and a south pole. Magnetic poles always come in pairs.

6. MAGNETIC FIELD Magnetic fields are areas where an object exhibits a magnetic influence. The Earth has a huge magnetic field. Because the core of our planet is filled with molten iron (Fe), there is a large field that protects the Earth from space radiation and particles. When you look at tiny magnets, they are working in a similar way. The magnet has a field around it. https://www.youtube.com/watch?v=8llkHQtaOlg (Magnetic Field Video) https://www.youtube.com/watch?v=7NrsLCsrxkU (Magnetism Video)

7. ELECTROMAGNETISM Electromagnetism is the relationship between electricity and magnetism. Magnetic fields are produced by moving charges (current). And moving charges are affected by magnets.

8. GREAT SCIENTISTS THINK ALIKE Electricity Creates Magnetism In 1820, the Danish physicist Hans Christian Orsted noticed something unusual while conducting experiments with electricity. He found that when an electric current was flowing in a wire, the needle of a compass placed nearby would move. The only thing that could do that was a magnetic field. Orsted had discovered that an electric current generates a magnetic field.

9. GREAT SCIENTISTS THINK ALIKE Magnetism Creates Electricity Michael Faraday, upon hearing of Orsted's discovery, believed that if electric currents could create magnetic fields then magnetic fields should be able to generate electric currents. In 1831, while carrying out a series of experiments designed to test his idea, Faraday discovered that a magnet moving near a wire could cause an electric current to flow in that wire. This is called a generator.

10. THINK ABOUT IT How did Hans Christian Oersted contribute to our knowledge of electromagnetism? How do the magnetic forces around a magnet vary? Why does a compass needle move when placed next to a wire carrying electric current? https://www.youtube.com/watch?v=nWY8SSdSBZo (Magnetic Toy)

11. SIZE OF BATTERY Car battery = About 12 volts. Double A battery = about 1.5 volts. A fully charged battery is like a boulder at the top of a hill. As electrical charges move around in a circuit, they pick up energy at the battery. The greater the voltage of the battery, the greater the amount of energy they pick up and the more energy is provided to the charged particles. A dead battery has no more energy that can be transformed. All of the energy has already been transformed into other types of energy.