16.5 - 16.6 Resistance Notes (Ohm's Law and Kirchoff's Law)

Definitions (words in bold in textbook):


Resistance: a measure of the opposition to current flow.
Ohm's Law: the principle that the electric current passing through a conductor is directly proportional to the potential difference across it.
Gauge number: the number on a wire that indicates its cross-sectional area
Series Circuit: a circuit in which the loads are connected one after another in a single path
Parallel Circuit: a circuit in which the loads are connected side by side and there are many paths
Kirchoff's current law: the law that states the total current at a point in the circuit equals the total current that flows out
Kirchoff's voltage law: the law that states that the total of all electrical potential decreases must be equal to the total of all electrical potential increases in a complete circuit
Conservation of electric charge & Conservation of energy: in any circuit, there is no net gain or loss of electric charge or energy

Info:
16.5 Resistance - Ohm's law

- Amount of current depends on two things: 1. the potential difference of the power supply 2. the nature of the pathway through the loads
- the more difficult the path, the more opposition there is to flow a.k.a. resistance
- when graphing Voltage vs. Current of a circuit, the slope of the graph ( V/I ratio) is constant. therefore the slope and the v/i ration must represent the resistance of the load because the resistance remained unchanged
- R = V/I, where R is given the unit "ohms" after Georg Simon Ohm who discovered this relationship
- Factors that determine resistance of a conductor:
     -   length
     -   cross-sectional area
     -   material that it is made of
     -   temperature


16.6 Series and Parallel Circuits


- Resistance in a series circuit
R = R1 + R2 + R3 .... + Rx

- Resistance in a parallel circuit
1/R = 1/R1 + 1/R2 + 1/R3 .... + 1/Rx