Chapter 8. Electricity and Magnetism

Electric charge is positive or negative; like charges repel and opposite charges attract. Electric current is the flow of charge, measured in amperes (A) [8][9].

Circuits. A circuit needs a source (such as a battery), conductors and a complete loop. In a series circuit there is one path and the same current through each component; in a parallel circuit there are several branches and the voltage across each branch is the same.

Key relationships

Ohm’s law: V = IR (voltage = current × resistance)

Electrical power: P = IV

Conductors and insulators. Metals conduct well; rubber, glass and plastics are good insulators.

Magnetism. Magnets have north and south poles; like poles repel and unlike poles attract. Moving charges create magnetic fields, and changing magnetic fields can induce currents. These links form the basis of electric motors and generators [8].

Electromagnetism. Electricity and magnetism are two aspects of one force, which unifies with light as electromagnetic waves.

Review: What current flows through a 4 Ω resistor connected to a 12 V battery? (Answer: 3 A.)