Presentation on theme: "Capacitors. First… How Does a Battery Work? A chemical reaction formed in a “CELL”. Slow but constant discharge. Kind of like an old person or turtle."— Presentation transcript:
First… How Does a Battery Work? A chemical reaction formed in a “CELL”. Slow but constant discharge. Kind of like an old person or turtle.
A battery is essentially a can full of chemicals that produce electrons – electrochemical reaction.
So HOW does it work? Positive Terminal Negative Terminal Electrons collect in the negative terminal A depletion of electrons is left on the positive terminal Current Flow Electrons flow from the battery into a wire, and must travel from the negative to the positive terminal for the chemical reaction to take place. That’s why batteries can Sit on a shelf for years and Still have power !
What do we use capacitors for?! Store whopping amounts of electrostatic energy Used to oppose changes in circuit VOLTAGE Deliver SMOOTH voltage throughout circuit, or holds up a voltage level (Prevents Voltage DIP) Getting back to business…
What do Capacitors look like? A family of capacitors…
Do Not EVER, EVER, EVER, EVER, EVER FORGET THIS! Never ever take your television set apart. EVER Capacitors are a special LEGOS as they are the only electrical device we use that stores electrical energy Like a Jack Rabbit or spring released all at once
What is Capacitance? Property of an electrical device that allows it to store an electrical charge. Or…..A “mighty” electrical spring
One way to visualize the action of a capacitor is to imagine it as a water tower hooked to a pipe. A water tower "stores" water pressure -- when the water system pumps produce more water than a town needs, the excess is stored in the water tower. Then, at times of high demand, the excess water flows out of the tower to keep the pressure up. A capacitor stores electrons in the same way, and can then release them later. Like a Water Tower
The difference between a capacitor and a battery is that a capacitor can dump its entire charge in a tiny fraction of a second, where a battery would take minutes to completely discharge.
The Electron Hole A positive ion attracts negative electrons. (that’s why electricity flows – to +) When an electron moves from its valance ring it leaves a “HOLE” A negative electron tries to fill the void while another electron fills another “hole” In a sense the “hole” moves
Let’s Make a HOLE!!! This demonstration will….. Explain why…….. 1.Electricity can travel so fast 2.How an electron hole forms 3.Capacitance and Potential Difference
Lightning as a HUGE Capacitor? Two Huge plates separated by a dielectric…..
How Big is BIG ? The coulomb is the international standard unit of electric charge, named after Charles-Augustin de Coulomb 1 coulomb is the amount of electric charge transported by a current of 1 ampere in 1 second… The amount of electrical charge in 6.241506×10 18 electrons 6,241,506,000,000,000,000 Capacitance is measured in Farads Farad = amount of capacitance for which a potential difference of 1 volt results in a static charge of 1 coulomb Or… the amount of capacitance that requires one second for a one ampere flow of charge to change the voltage by one volt.
1 Farad = The amount of capacitance that requires one second for a one ampere flow of charge to change the voltage by one volt A standard alkaline AA battery holds about 2.8 amp-hours. That means that a AA battery can produce 2.8 amps for 1 hour at 1.5 volts. There are 3,600 seconds in one hour. To store one AA battery's energy in a capacitor, you would need 3,600s * 2.8A /1.5v = 6,720 farads!! Howstuffworks.com Obviously, it's impractical to use capacitors to store any significant amount of power unless you do it at a high voltage.