Electric Current 6.2. Current and Voltage Difference Electric Current-The net movement of electric...
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Transcript of Electric Current 6.2. Current and Voltage Difference Electric Current-The net movement of electric...
Current and Voltage Difference
Electric Current-The net movement of electric charge in a single direction. Measured in Amperes (A)
One Ampere is equal to 1 coulomb per second
If there is no current, there is no NET movement Movement forward=movement backward=movement side-to-side
When an electric current is applied, there is still backward and forward movement, but the electrons drift in the direction of the current. Net movement
Current and Voltage Difference
Related to the force that causes electric charges to flow. From area of high voltage to low voltage
Measured in volts (V)
Electric Circuits A closed path that electric current follows
Battery, wire, lightbulb
Current and electron flow For historical reasons, we think of current as flow of positive charges
Positive charges do not flow
Due to this, current is in the opposite direction of electron flow
Electrons flow from lower to higher voltage
Current is from higher to lower voltage
Dry-Cell Batteries
Carbon Rod (positive)
Zinc Container (negative)
Moist paste (electrolyte)
Allows electrons to flow
Batteries in flashlights
Metals can be different
Lithium, carbon, and lithium
solution
Cell phone battery
Wet-cell Battery
2 connected plates made of different metals in an electrolyte
Unlike the paste in dry-cells, the wet-cell has a liquid
Has many cells connected together.
Most common type is lead-acid
Lead and Lead dioxide in sulfuric acid solution
Resistance
Tendency of object to resist flow of electrons Takes some of the flowing electrons from the current
Measured in ohms (Ω) This symbol is the capital form of the Greek letter “Omega”
This is why batteries charging get warm The resistor is taking some of the electrons, and converts the
chemical energy to thermal energy
Ohm’s Law
Current(A)=Voltage difference(V)/resistance(Ω) Current is measured in Amps (A)
Where I is current
Example Problem
The voltage difference in a graphing calculator is 6V, and the resistance is 1,200 Ω. What is the current through the batteries of the graphing calculator?
Knowns: V=6V, R=1200 Ω
Unknown: I=?
Equation:
Solve:
=0.005 A
Guided Practice
An object has a resistance of 60 Ω as a current of 2 A goes through it. What is the voltage difference across the object?
You Try It!
The voltage in a device is 50 V, and the resistance is 5 Ω. What is the current in the device?