P4.2.1 Electrical charge

Characteristics of charge

• Electric charge (Q) can be positive or negative

  • Opposite charges attract, like charges repel

  • Measured in Coulombs (C) or millicoulombs (mC)

  • mC to C → divide by 1000

  • C to mC → multiply by 1000

What is a conductor? Provide examples

• Conductors:

  • Materials that allow electrical charge to move freely

  • Examples:

    • Metals (have delocalised electrons that can move to conduct electricity)

      • Silver

      • Gold

      • Copper

      • Steel

      • Sea water (NaCl dissolves and acts as an electrolyte)

What is a semiconductor? Provide examples

• Semiconductors:

  • Materials that are poor conductors when cold, but better when warm

  • Examples:

    • Silicon

    • Germanium

What is an insulator? Provide examples

• Insulators:

  • Materials that do not allow electrical charge to move freely

  • Examples:

    • Wood

    • Rubber

    • Glass

    • Oil

    • Diamond

Describe how electrostatic charge occurs

• Electrostatic charge can be produced by friction

  • When 2 insulating materials rub against each other, electrons may be transferred

  • The material that gains electrons will become negatively charged

  • The material that loses electrons will become positively charged

Describe methods for detecting electrostatic charge

• Putting charged object near paper scraps and watch paper scraps be attracted to object

• Putting charged object near water stream and watch stream bend

What is an electric field?

• A region in which an electric charge experiences a force

• An electric field always points in the direction in which a positive charge experiences a force

  • If the positive charge is pulled to the right, field lines point to the right, and vice versa