Presentation on theme: "I. is a force defined as the movement of negatively charged electrons."— Presentation transcript:
I. is a force defined as the movement of negatively charged electrons.
A. Types of Electricity 1. Static is not moving. An example of this would be a person rubbing his feet against carpet and touching a conductor. What is a conductor? A conductor is something that allows electricity to flow.
a. Lightning Why do we see lightning before we hear thunder? Since light and sound travel at different speeds, we see the lightning before we hear the thunder. They occur at the same time, however.
2. Current Electricity Also known as moving or electric energy. Electricity needs a force to push the electrons into a flow (batteries or generators).
II. Conductors vs. Insulators Conductors allow electricity to move through them. Insulators do not allow electricity to move through them. Give an example of a conductor. Copper, water, and aluminum are good conductors. Give an example of an insulator. Plastic, wood, and glass are insulators,
Which is best to hold if I am heating a liquid in a metal pan?
A. Current Current is the amount of electrons passing through an area at one time. It is measured in Amps. Current may be direct (DC) or alternating (AC). Alternating current moves in one direction and then moves in the opposite direction, switching back and forth in direction.
Direct Current If an alternating current switches directions, how does direct current move?
Why have two types of current? It allows us to transport energy more efficiently over a greater distance.
B. Resistance This is the force NOT allowing electrons to move easily. It is measured in Ohms. Question: Something with a low resistance is a good conductor. True or false? Give an example of a conductor.
1. Insulators An insulator does NOT allow electrons to move through it easily. We use copper as a conductor in our electrical plugs.
Insulators Electrical plugs are coated with an insulator. What is the insulator? Why is it needed? Electrical plugs are coated with an insulator. What is the insulator? Why is it needed?
III. How do we get electrons moving? Forces that start the flow of energy: Batteries can do this. They store chemical energy. One end of the battery contains extra electrons (so it will have what type of charge?) The opposite end of the battery has too few electrons (so it will have what type of charge?)
A. Units of Energy Amps = Current is the amount of electrons passing through an area at one time. Ohms = Resistance or the force not allowing electrons to move. Watt = energy used per second Voltage = Current (I) x Resistance (R)
Resistance Human body has a resistance of 500,000 Ohms if dry. Human body has a resistance of 100 Ohms if wet. Salt lowers resistance even more. Why is it not a good idea to be in a tub during a thunder storm?
Why is this not a good place to be during a lightning storm? The chance of electrocution is increased drastically. The tub may also be connected to a metal pipe that runs to the ground.
B. Circuits are the paths for electrons: 2 types Series – all energy flows through the same path (like x-mas lights, if one goes out they all go out) Parallel – energy flows to each bulb (like in your homes)
When you flip a light switch, you complete the circuit. The electrons (chemical energy) are sent through a light bulb (which has a high resistance) and heat energy is produced. Heat energy changes to light energy.
What’s in your bulb? At the bulb base, bulbs have two metal contacts, which connect to the ends of an electrical circuit. The metal contacts are attached to two stiff wires, which are attached to a thin metal filament. The filament sits in the middle of the bulb, held up by a glass mount. The wires and the filament are housed in a glass bulb, which is filled with an inert gas, such as argon.
Moving current… When the bulb is hooked up to a power supply, an electric current flows from one contact to the other, through the wires and the filament.
How do electrons move??? As the electrons zip along through the filament, they are constantly bumping into the atoms that make up the filament. The energy of each impact vibrates an atom -- in other words, the current heats the atoms up. It’s almost like a domino effect. One atom moves, so another moves, and another, and so on.
What are photons? Bound electrons in the vibrating atoms may be boosted temporarily to a higher energy level. When they fall back to their normal levels, the electrons release the extra energy in the form of photons. Metal atoms release mostly infrared light photons, which are invisible to our eyes. But, if they are heated to a high enough level -- around 4,000 degrees Fahrenheit (2,200 degrees C) in the case of a light bulb -- they will emit a good deal of visible light.
How much metal is in my bulb??? The filament in a light bulb is made of a long, incredibly thin length of tungsten metal. In a typical 60-watt bulb, the tungsten filament is about 6.5 feet (2 meters) long but only one-hundredth of an inch thick. The tungsten is arranged in a double coil in order to fit it all in a small space. That is, the filament is wound up to make one coil, and then this coil is wound to make a larger coil. Tungsten is used in nearly all incandescent light bulbs because it is an ideal filament material.