Transcript Template Title - University of Oklahoma Physics

Insulators and Conductors
• Electric Circuit
– Current provided by battery flows through wire, into the
light bulb, through another wire, and back to the battery.
• Current: flow of electrons
Battery
•Pencils
Electric lamp
(not glowing)
Electric lamp
(glowing)
Conductor
lets electrons flow
Insulator
doesn’t let electrons flow
are a good demo, touch the wires to the wood (no light), then
touch them to the graphite (the LED lights up).
•Try sliding the loose ends of the wires closer & farther, it may effect the
LED’s brightness -more distance the higher the resistance in the circuit.
•The Multi-meter isn’t so much for the testing of conductivity in this
instance, it can be but the numbers usually loose the kids. It mostly
serves to show the older kids that conductivity/resistance can be directly
quantified.
Applications of Insulators and Conductors
High-Tension wires
Superconductors
Zero Resistance Infinite conductivity
Only at very low Temperature
High-Voltage Transmission Lines:
Up to 765,000 Volts
Wires are Copper
Insulators are ceramic
(they used to be glass).
High-Voltage
Breakdown
Insulators
Computers have printed
circuit boards with copper
lines connecting different
Silicon chips.
Silicon is a
semiconductor it can
conduct or insulate
Atoms
Insulators and Conductors
Free electrons from outer shells of metal
atoms can move throughout material
Conductors let
electrons go. They
travel anywhere in
the material.
Metal ions (+) remain stationary
Insulators let electrons flow
like dogs running free
There are NO free electrons, electrons
are shared between atoms in bonds.
Insulators hold
electrons close like a
dog on a leash
Metal ions (O) remain stationary
Conductors let electrons
flow like dogs running free
Resistance: is like
resistance to
water flow in a
hose. Larger
diameter hose less resistance,
longer hose –
more resistance
Voltage like
pressure,
current like flow
Resistance
• Resistance: How much the material resists the flow of
electrons
R=V/I
• The higher the resistance, the slower the flow of
electrons, the smaller the power output
Higher Resistance
R = ( x L) / A
R - Resistance
 - Density
L - Length
A - Area
Lower Resistance