Current Electricity

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Transcript Current Electricity

Current Electricity
Electric Potential Difference
• Electric potential is the amount of energy per
amount of charge
• A large amount of potential energy at a place
where large amounts of charge are present
results in a large electric potential
• A small amount of energy for a given amount of
charge results in a small electric potential
• The difference between two such points (one
high potential and the other low) is called electric
potential difference
Batteries
• In 15 seconds, list the many devices you have
used this morning that required a battery.
How many could you come up with?
Light It Up
Materials: 1 bulb, 2 alligator clips, 1 battery
Task 1: Using the materials provided, find at
least 3 ways the bulb can be lit
Task 2: Diagram the 3 ways you were able to get
the bulb to light
Task 3: Diagram at least 3 ways in which you are
not able to get the bulb to light
Analysis: What causes the bulb to light?
What is a Battery?
• A mobile source of power called a voltaic cell
• Italian physicist Alessandro Volta created the
first battery by stacking alternating layers of
zinc, brine-soaked cloth, and silver.
• This arrangement was called a voltaic pile
• The first device to have a lasting current
• The first commercial battery was sold in the
US in 1898 by the Eveready Battery Company
(Energizer)
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Anatomy of a battery
Every battery has 2 terminals,
positive and negative
A cathode connects to the
positive terminal
An anode connects to the
negative terminal
Generally known as electrodes,
the terminals are where
chemical reactions occur
The medium that allows the
electric charge to flow between
the cathode and anode is
known as the electrolyte.
Electron Flow
• We call the flow of electrons electric current
• The chemical reactions in the battery create
free electrons and positive ions
• It is the flow of electrons that cause a lamp to
light
• Electrons actually flow from the negative
terminal to the positive terminal
• Electrons flowing in this direction is known as
electron flow
Conventional Current
• Originally the thought was that positive charges
could move
• Conventional current assumes that positive
charges move from the positive terminal to the
negative terminal
• We now know this is not true, but the convention
indicating the direction charges flow remains
• http://www.youtube.com/watch?v=Y7Uqe6DyoRU
• http://science.discovery.com/videos/deconstructed-how-carbatteries-work.html
Circuits
• The electrons flow when a path is
present between the terminals
• We call this closed loop an electric circuit
• Electric energy is converted to other
forms of energy including kinetic energy,
light energy, or heat energy
Diagramming Circuits
• A schematic is a drawing of an electric circuit
Standard symbols include
Conducting Wire
Fixed Resistor
Switch
Battery
Voltmeter
(measures potential difference)
Ammeter
(measures current)
Electric connection
Lamp (light)
Example