Transcript File
Electrical Principles & Technologies Lesson Objective: Students will distinguish between static and current electricity and identify evidence of each. Electrical Energy Tesla Coil: Nikola Tesla, one of the pioneers of electricity. Jacob’s Ladder: Video Static Electricity Lightening and the sparks you might see when you pull a sweater over your head in a dark room are both examples of static electricity. We often call it “getting a shock” when we feel these jolts of electricity, but is is the same electrical force that causes lightening. Same force that clothes to “cling” together. Thales’ Amber Around 600BC, Thales was the first person known to experiment with static electricity. Found that by rubbing amber (fossilized tree resin) it caused it to attract some things. Electricity comes from the Greek word for amber- electron The explanation of static electricity begins with the atom. Remember… Some particles in the atom are electrically charged. Proton: has a positive charge. Electron: has a negative charge. The charges on the particles can cause either attractive or repulsive(pushing away) forces between the particles. Our quick lab… Rubbing the balloon against your hair causes the balloon to steal electrons. Opposites Attract Opposite charges attract each other- this is why after rubbing a balloon on your hair/clothes it will stick to a wall. Like charges repel Two equally charged particles will push away from each other if they are brought close together. Most objects have equal amounts of positive and negative charges… Which makes them neutral. Sometimes an object has more than one type of charged particle than another. Built up static charge. Static means not moving or stationary. This type of charge does not flow like the electrons in an electrical current. Charge Separation When a charged object-like the negatively charged balloon after it is rubbed in your hair-is brought toward a “neutral object” - like a wall that you bring the charged balloon toward- the negative charge of the balloon repels the electrons in the wall, leaving the area of the wall closest to the balloon positive. The balloon and the wall are attracted because of these opposite charges. Electrical Discharge Static electricity does not flow like a current, but it does sometimes discharge. Built up charge may be attracted to another object and “jump” Electrical Discharge The spark resulting from the shock you feel, or the spark you see when you drag your feet across a carpet and touch someone is referred to as electrical discharge. Van De Graff Generator (VDG) Scientists use VDGs to study electrical discharge. They build up a static charge using friction- transfers to you when you touch the sphere. Current Electricity “Electric eel”- can discharge enough electricity to kill a human being. Electroplaques- modified muscle cells that can produce electricity. Releases electricity to kill or stun prey, for defence, and for communication. Electric Eel electricity: Similar to static charges- they build up and discharge, but they do not flow continuously. The steady flow of charged particles is called electrical current. Circuits Electrical current is the type of electricity that powers electric devices. Flows continuously if 2 conditions are met: 1. Flow of electricity requires an energy source. 2. Electrical current will not flow unless it has a complete path or circuit for the charged particles to flow through. Amperes The rate at which an electrical current flows is measured in amperes (A) Named in honour of AndreMarie Ampere. Why won’t my curling iron work in Europe?:( Most electrical devices in our home have a current of less than 15A Microwave- between 5 and 8 A 60 W Light bulb- 0.5 A Electric kettles- 13 A Digital watch- fraction of an amp here Electric Charges Can be produced by devices ranging from miniature cells in watches, to huge generators in power stations. Conductors How do we move the charge from where it is produced to where it is needed? There are many materials that electrical charge can move through easily. Such materials are called conductors. Conduction of electricity through wires allows for the transfer of electrical energy from place to place. Circuits are paths that control the flow of electricity. In most electrical circuits, the path that the electricity flows along is made of solid metal wires. Circuits can also include gases, other fluids, or other substances. Load A circuit usually includes a conductor, and energy source, and a load. A load is a device to convert electrical energy to another form of energy. A light bulb is a load that converts electrical energy into light and heat. Electrical Energy Is the energy carried by charged particles. Voltage is a measure of HOW MUCH electrical energy each charged particle carries. The higher the voltage: The greater the potential energy of each particle. Potential Difference Voltage is also called “potential difference”. The energy delivered by the flow of charged particles is equal to the voltage times the total charge of the electrons. Volt(V) The unit for voltage is the volt(V) Named for Italian physicist Alessandro Volta For safety reasons… Most voltages in everyday devices are fairly low. Flashlights- 6 V Cars- 12 V electrical systems Wall sockets- 120 V Industrial machinery- 600 V Electrical transmission lines- 100kV Measuring Voltage Voltmeter- simplest way to measure voltage. Many have sensitive needles that can be damaged if connected improperly. Red-Positive Black-Negative Some voltmeters have more than one red terminal. Start with the highest and work down until you get a clear reading. Millivolts Each millivolt is 1/1000 of a volt. There are many different kinds of voltmeters; some digital. Can also connect some to computers. St. Elmo’s Fire Sailors saw a glow around the tips of ships’ masts before storms and called it St. Elmo’s fire. High-Voltage transmission lines sometimes have an erie blue glow; now called Corona Discharge.