Conductors

• Conductors contain free charges that easily move

• When extra charges are present, they quickly move to places where the electric field is perpendicular to the surface

  • Then they stop moving

  • This is electrostatic equilibrium​

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Conductors in Electric Fields

• A conductor in an electric field will polarize

• Inside the conductor, electric field = 0

• Just outside of the conductor, electric field is perpendicular to the surface

• Any excess charge resides on the surface​

  • ​Charges on the surface space themselves as far apart as possible

Uneven Conductor Surfaces

• If the surface is uneven, more charge will collect near the area of most curvature

• If the curve is great enough, the electric field can be strong enough to remove excess charge

  • Lightning Rods

  • Also why you NEVER put forks or other metal utensils in the microwave.​

Shielding

• Conductors shield any charge within it from external electrical fields

• Sensitive or critical electrical equipment is shielded by putting it in a metal box​

  • i.e. Faraday Cage

• ​Coaxial cables are shielded by a metal cylinder around the central metal wire

  • This reduces interference and signal loss​

Applications

Copiers work by charging toner particles and paper using conductors.

1. The drum is given a positive charge.

2. Lenses and mirrors shine an image onto the drum.

   1. Where the light hits the drum the selenium conductor becomes neutralized.

   2. Where the image is dark, the positive charge remains.

3. Toner is given a negative charge and sticks to the drum.

4. The paper is given a huge positive charge so toner sticks to the paper.

5. Paper is then heated to melt the toner.​

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More Applications

Laser Printer

• Similar to copier but the image is put onto the drum by lasers

• The laser scans the drum quickly

  • ​The computer turns the laser on/off at the right time to produce an image