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Electric Current SECTION 2.  The net movement of electric charges in a single direction is an electric current  Electric current is measure in amperes.

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Presentation on theme: "Electric Current SECTION 2.  The net movement of electric charges in a single direction is an electric current  Electric current is measure in amperes."— Presentation transcript:

1 Electric Current SECTION 2

2  The net movement of electric charges in a single direction is an electric current  Electric current is measure in amperes (A)  One ampere is equal to 6,250 million billion electrons flowing past a point every second  Electric charge will flow where there is a voltage difference  Voltage difference is measured in volts Current and Voltage Difference

3  A path that an electric current follows is a circuit  A circuit path must be closed  If a circuit path is broken, current will not flow  What happens when you flip off a light switch?  The circuit is broken Electric Circuits

4  To keep electricity flowing, a voltage difference must be maintained  A battery can supply that voltage difference  Dry Cell Battery  Consists of two electrodes surrounded by an electrolyte  The electrolyte allows charge to move from one electrode to another  In a dry cell the electrolyte is not a liquid Batteries

5  Wet Cell Batteries  Contain two connected plate made of different metals or metallic compounds in a conducting solution  A wet cell batteries contains many wet cells connected together  Lead-Acid Batteries  Most car batteries  Contains 6 wet cells  Lead and Lead Dioxide plates  Sulfuric Acid solution Batteries

6  When electrons flow through a material, the material will offer some resistance to the flow of electrons  Resistance is due to collisions of the electrons with atoms in the material it is flowing through  Some of the electrical energy of the electrons is converted to thermal energy  Sometimes the resistance is great enough that it causes the material to glow  Flashlight filaments  Most materials offer some electrical resistance (except super conductors)  Electrical conductors offer less resistance than electrical insulators Resistance

7  Temperature, Length, and Thickness will affect resistance  Resistance tends to increase as temperature increases  Resistance tends to increase as the distance traveled (length of the wire) increases  Resistance tends to increase as the wire becomes thinner  How could you manipulate a metal filament to become more resistant?  Coil the metal to increase length  Use thin wire  Why would you want to?  Filament must glow so resistance must be high Resistance

8  Simple circuit has  A source of voltage difference  battery  A device that has resistance  light bulb  Conductors that connect the device to the battery terminals  wires The Current in a Simple Circuit

9  Resistance, current, and voltage difference are related.  The relationship is known as Ohm’s Law  The current in a circuit equals the voltage difference divided by the resistance Current (in amps) = voltage difference (in volts) resistance (in ohms) I = V/R Ohm’s Law

10  Calculate the voltage difference in a circuit with a resistance of 25 ohms if the current is 0.5A  12.5 Volts Ohm’s Law

11  A current of 0.5 A flows in a 60-W bulb when the voltage difference between the ends of the filament are 120 V. What is the resistance of the filament?  240 ohms Ohm‘s Law


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