Energy Transformations Electricity and Magnetism Electricity: the transfer of energy in the form of negative charges. It is important to understand that we do not MAKE electricity. We convert other forms of energy into electricity (kWh). Rule #1: Like Charges Repel One Another Rule #2: Opposite Charges Attract To understand electric charge you need to understand atomic structure! Here is a quick review: Atoms have positively charged nuclei The nucleus contains protons (+) and neutrons (o) The particles in the nucleus make up the mass of the atom (mass #) Electrons (-) surround the nucleus in energy levels Electrons are so small that their mass is negligible In a normal state, the number of protons and electrons is equal An ion is an atom with a charge Gaining electrons causes a negative charge (anion) Losing electrons causes a positive charge (cation) When an item is charged NO ELECTRONS ARE CREATED OR DESTROYED! They are simply transferred from one material to another! Law of Conservation of Matter Coulombs Law The Force Between Charged Particles Increases with decreasing distance Increases with increasing charge magnitude Coulombs Law is like Newton's Law of Gravityexcept the forces can be attractive or repulsive. This force is responsible for holding an e- in orbit around the positive nucleus. Charge Polarization A polarized object has no net charge. However, the distribution of the charges is altered. We know that opposite charges attract and like charges repel. However, we also find that a charged object is attracted to an uncharged object (such as your finger)! If we bring a conductor close to the charged object, electric charges can flow from one part of it to another, Voltage: electrical pressure When water flows in a pipe there is more pressure on one end than the other. There must be a pressure difference to keep the water flowing Voltage is directly proportional to electric potential energy Electrons and other charged particles have energy due to their positions An increase in PE is due to work input F + ++ F + Electric Current: the flow of electric charge due to a difference in voltage The rate of electrical flow is measured in amperes Electrons flow in a way similar to water flow. Water current is the direction of water flow Electric current is the direction of electric flow Electrical Resistance: Just as narrow pipes resist water flow more than wide pipes, narrow wires resists electrical current more than thick wires. Copper has a very low resistance while a strip of rubber hs a very high resistance The lower the temperature the lower the resistance The resistance of some materials reaches zero at very low temperatures. These are SUPERCONDUCTORS Ohms Law: the relationship between Current, Voltage and Resistance Current = Voltage/ Resistance Electrical Power Measured in watts or kilowatts The rate that energy is converted from one form to another P = I V or Power= Current x Voltage From Mechanical to Electrical Energy Moving charges like those in an electric current, produce magnetic fields and moving magnetic fields create electric current. The Faraday Effect Magnets Copper Wire Motion Electricity Electric Field: region where charged particles can be pushed or pulled Magnetic Field: surrounds an electric current Electric Generators A generator produces electric current by rotating a coil of wire in a magnetic field. This process is called electromagnetic induction. G Mechanical Energy Electrical Energy 1.Wind moves against the blades of a wind turbine. 2.The energy forces the propeller to spin which subsequently spins a generator inside the turbine.generator 3.As the generator is rotated, the magnets that are moving around an electrical wire inside the turbine causes electrons to move through the wire. 4.Thus, electricity is created out of wind energy by the wind turbine. Connection to Wind Energy Electric Motors An electric motor is a device that changes electrical energy into mechanical energy. It contains an electromagnet that is free to rotate between the poles a permanent fixed magnet. The coil of the electromagnet if attached to an electrical source M Electrical Energy Mechanical Energy A battery or generator moves electrons in a circuit. The amount of current depends on the voltage and the resistance of the circuit The Electromagnetic Spectrum energy that can travel through space in the form of waves even when no matter is present Electromagnetic Waves When the electric field changes (accelerates or decelerates) so does the magnetic field causing an electromagnetic wave. The accelerated electrons give off energy of varying wavelengths. Electric Field A region in which a charged particle can be pushed or pulled Magnetic Field A region in which magnetic forces are present The Electromagnetic Spectrum All electromagnetic radiation travels at the same speed, but at different wavelengths