1. Resistance in Electrical Systems
4.3 Notes
Resistance in Electrical Systems

2. Properties of Materials
Conductors
Insulators
Have a large ability to conduct electric current
They contain many free electrons
Metals are good conductors
Temperature influences resistance of the flow
What happens to the energy when resistance is present in electrical systems?
Have a lower ability to conduct electric current
Electrons are tightly bound
Nonmetals are good insulators
What are semiconductors?

3. Variables and Units of Electricity
Voltage (potential difference)- the ability to accelerate an electric charge between two points in an electric field.
Measured in VOLTS
Current- the rate of flow in a conductor.
Measured in AMPERES
Resistance- measure of the ability of an electrical device to oppose flow of charge through a device
Measured in OHMS (Ω)

4. Ohm’s Law R = ρ(L/A) Measured in (Ωm)
V = IR Voltage = (current) (resistance)
I = V / R Current = (voltage) / (resistance)
R = V / I Resistance = (voltage) / (current)
Resistivity- a property of a material that describes its ability to resist flow of electric charge
Resistivity is a physical property of individual materials and is influenced by temperature.
R = ρ(L/A)
Measured in (Ωm)

5. Types of Circuits Series Parallel
A circuit with only one path for the current to flow
RSERIES= R1 + R2, R3+…
A circuit in which there are multiple paths for the current to flow
1/RPARALLEL = 1/R1, + 1/R2 + 1/R3+ …

6. Resistors
R = (First digit * 10 + second digit) (multiplier)