Download 4.3 Notes - Seymour ISD

4.3 Notes
Resistance in Electrical Systems
Properties of Materials
Conductors
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?
Insulators
Have a lower ability to conduct
electric current
Electrons are tightly bound
Nonmetals are good insulators
What are semiconductors?
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)
Types of Circuits
Series
A circuit with only one path
for the current to flow
Parallel
A circuit in which there are multiple
paths for the current to flow
RSERIES= R1 + R2, R3+…
1/RPARALLEL = 1/R1, + 1/R2 + 1/R3+ …
Ohm’s Law
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)
Resistors
R = (First digit * 10 + second digit) (multiplier)