Conductivity
Conductors, insulators, charge carriers, and how current moves through materials
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Plasma - 4th State of Matter
School blocks YouTube? Use the file below.
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plasma_ball.mov |
Most people view electricity
Download Animation (bulbs.zip - 240 KB)
Batteries don't supply the electrons Instead, they create an electric field that 'pushes on'
Alessandro Volta's electric battery prototype (18 century)
Show Me The Physics
Print these Fill in the Blank Notes Electric Current - stream of electrically charged particles passing through a given area (movement of electrons in a wire
A) Conductivity of Solids 1) Metals - contain many free electrons (good conductors)
2) Glass, fused quartz, rubber - good insulator Few free electrons Insulators have a High Resistivity
3) Semiconductor - a material with a resistance between conductor and an insulator
B) Conductivity of Liquids
1) pure liquids don’t conduct
2) liquid with dissolved ions conduct
(electrolyte solution)
(ion movement transfers charge
Ions transfer charge in living things
C) Conductivity of Gases
Gases conduct when ionized (charged) when exposed to:
a) high energy radiation
b) OR electric field
c) OR with collision with high speed particles
Charge in a gas is transferred by ions and electrons
Plasma–very hot ionized gas
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Check Your Understanding
5 quick questions — pick an answer to see if you’re right.
1. Why are metals such as copper good conductors of electricity?
2. Glass, fused quartz and rubber are good insulators. What do they have?
3. Which liquid would conduct electricity best?
4. A friend says a battery supplies the electrons that flow through a wire. What actually happens?
5. Plasma, the 4th state of matter that makes up stars, is best described as:
Choosing a Material for Wires
Engineers choose wire materials based on resistivity, cost, and mass. Table 1 shows the resistivity of several materials at 20 °C.
Table 1: Resistivities at 20 °C
| Material | Resistivity (Ω·m) |
|---|---|
| Silver | 1.59 × 10−8 |
| Copper | 1.72 × 10−8 |
| Aluminum | 2.82 × 10−8 |
| Tungsten | 5.60 × 10−8 |
| Nichrome | 150. × 10−8 |
Which material is the best electrical conductor?
▶ Want a challenge? Open 6 more Regents-style questions (harder · mixed formats)
Challenge score: 0 / 6
C1. A student makes the following claim.
Place a check mark in either the Support or Refute box. Justify your response using a mathematical relationship.
C2. Most household wiring is copper rather than silver. What is the best explanation?
C3. A toaster heating element is a nichrome wire 2.0 m long with a cross-sectional area of 1.0 × 10−7 m². Substitute numerical values into a mathematical representation that can be used to determine the resistance of the element. Then calculate the resistance.
C4. Wires of identical length and thickness are made from each material in Table 1. Place a check mark in two boxes to indicate the materials whose wire would have more than twice the resistance of the copper wire.
C5. Which material would be the best choice for a toaster’s heating coil?
C6. Aluminum is about one-third as dense as copper (2.70 g/cm³ vs. 8.96 g/cm³). Using this fact and Table 1, identify one benefit and one drawback of using aluminum instead of copper for long-distance power lines.