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B. 5 Current and Circuits - Coggle Diagram
B. 5 Current and Circuits
Voltage
Represents the potential difference between 2 points
1 volt impacts 1 joule to move 1 coulomb of charge
V=J/C
Voltage is also called potential difference o electromotive force
Measured in Volts (v)
Current -
Conventional current flow from positive to negative, even though electrons flow from the cathode to the anode.
Electrons can only flow through conductors (ex. metal wire)
Current is the flow of electric charge (electrons)
Current it measured in amperes (A)
Increasing voltage or decreasing resistance increases current
Resistance
Metals have low resistance, which makes them good conductors.
Ohm's law examines the relationship between current and voltage through the same material. It shows that they are directly proportional. The constant was named "resistance" and is specific to certain materials.
An object with high resistance obstructs the flow of current
From Ohm's law, we get the equation V=IR
Resistance is how well an object opposes the flow of current
Resistance is directly proportional to length and inversely proportional to cross sectional area of a wire.
Power
The rate at which electrical energy is transferred
Energy = Power * Time
P=VI, but there are other ways to express it
Power is measured in watts (W)
Resistors consume power, the dissipate energy in the form of heat
Potential divider
A potential divider is a special type of circuit with a constant voltage and 2 resistors (R1 and R2)
R2 is generally a variable resistor
The potential difference of the battery is "divided" among the two resistors
Imagine if R2 is a light dependant resistor. As the light increases, its resistance decreases. This would cause the reading on the voltmeter to decrease.
If you attach a voltmeter in series to R2, you can see how much potential difference is used up by that resistor
As shown in the above example, potential dividers convert changes to resistance into changes in voltage. This is useful to measure changes in environmental conditions.
Internal resistance
A real batter can be imaged to contain a perfect cell + a small resistor
It is possible to calculate the internal resistance using the equation V=-IR+r
However, batteries aren't perfect conductors. They have some resistance, this is called internal resistance or internal chemical resistance (because resistance is caused by chemical in the battery.
Plot the graph for the equation
Batteries provide electromotive force in a circuit
The Y intercept is the internal resistance