Notes: Ohm's Law and Kirchoff's Laws
Summary of Concepts and Definitions
n An electric circuit consists of a voltage source, a conductor, and a load.
n The current path in an electric circuit can be
ð Series in which there is only 1 path for current to flow
ð Parallel in which there are multiple paths for the current to flow
ð Series-Parallel combination in which there are a combination of series and parallel paths for the current to flow
n The current flow in the circuit can be changed by changing either the voltage or the resistance
n Current, voltage, and resistance are related in all circuits by Ohm's law: V = IR
Note that Ohm's law is true for any point in a circuit and can be applied at any time
n A junction is defined as any point of a circuit at which two or more current paths meet.
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n Kirchoff's 2 laws
ð They are conservation laws that deal with conservation of charge and energy.
Both circuit laws can be directly derived from Maxwell's equations but Kirchoff preceded Maxwell. Kirchoff generalized work performed by Georg Ohm.
ð Current law: First Law - Conservation of Charge
The total current flowing into a junction is equal to the total current flowing out of that junction
ð Voltage law: Second Law - Conservation of Energy
The total voltage drops in a closed circuit equals the total voltage source (the voltage rise). It is also sometimes stated as the equality of the total voltage rise is equal to the total voltage drop.
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