Basic Linear Circuits Review

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Common Measurements and Units

In the representations of measurements such as charge, voltage, current, and power, an uppercase letter (C, V, I, P) implies that it is constant, and a lowercase letter (c,v,i,p) implies that it is time-variant.

Charge (Coulomb)

Protons are positive charges, and electrons are negative charges. Charges in motion is a current. The SI unit for charge is the coulomb, which is equivalent to the amount of charge the current (in amperes) delivers in an amount of time (in seconds). 1 coulomb is equal to 1 ampere multiplied by 1 second.

1C=(1A)(1s)

Electric Poential (Volt)

The volt is a unit for the relative potential energy between two points or two electrodes. The ground is usually assigned a voltage of 0, and used as a reference. Current tends to flow from high voltage to low voltage. 1 volt is equal to 1 Joule per Coulomb.

1V=(1J)/(1C)

Current (Ampere)

An electric current represents electric charges flowing through a conductor. By tradition, the current is modeled as a flow of positive charges, even though it was later discovered that current is in fact a flow of negative charages. The ampere, or amp, is the unit for the current, and is determined by the rate of flow of the charges. 1 amp is equal to 1 coulomb per second.

1A=(1C)/(1s)

Common Electrical Components

Symbols, Variables, and Units
symbol variable units
current source File:Current source symbol.jpg I Ampere (A)
voltage source File:Voltage source round symbol.jpg or File:Voltage source batt symbol.jpg V Volt (V)
resistor File:Resistor symbol.jpg R Ohm ()
capacitor File:Capacitor symbol.jpg or File:Capacitor polarized symbol.jpg (polarized) C Farad (F)
Inductor File:Inductor symbol.jpg L Henry (H)