Current (I) The rate of flow of electrons from one point to another. –Coulombs/second = C/s = Amperes (A) More AmperageLess Amperage More AmperageLess Amperage Electrons in wires

Current DC (direct current) only allows current to travel in one direction (what we study) AC (alternating current) is when current pulses back and forth in both directions in a circuit. Current always travels the path of least resistance… –Current will take the easiest path it can –If it can avoid resistance, it will (short circuits)

Resistance (R): the measure of how strongly an object impedes current. Units: Ohms (Ω) Resistors are designed to have a specific resistance. (almost anything you “plug in” to a circuit provides resistance) In our simple circuits they look like this: All these are also types of resistors:

Factors Affecting Resistance Although wires do have resistance it is very small, especially if you use short, thick wires made of good conductive material.

Potential Difference aka Voltage (V), is the work required to move a charge from one location to another. In a circuit, voltage is provided by a battery or power supply, which provides a PUSH to the charges. Units: Joules/Coulomb = J/C = Volts (V)

Conventional Current Benjamin Franklin did a lot of the foundational work in understanding charges. He thought that protons (+) moved and therefore diagrams motion of particles from the positive to the negative. We use this convention when labeling the flow of charge in a circuit.

Electron Flow Now we know that Franklin was wrong. Electrons (-) are the charges that are mobile. Actual motion of the charges are from negative to positive, but we still diagram using conventional current notation.

Voltage Gain Voltage is “gained” as charges move past the battery. –Within the battery there is a positive and negative end, charges are pushed from the negative side of the battery, out through the circuit, back to the positive side of the battery. –Every time electrons pass through the battery they gain energy.

Voltage Drop Voltage is “used up” as it moves through the circuit, and only returns after passing through the battery again. –Voltage is used because the charges do work when they move through the resistor and cannot be re-energized until passing back through the battery. –All the energy that the electrons gained in the battery is used up by the resistors before returning to the battery.

Ohm’s Law explains the relationship between Current, Voltage, and Resistance Voltage is directly proportional to current. Resistance is inversely proportional to current.

Ohm’s Law