Electricity and Static Electricity Basics

Electricity

• Electricity is the flow of electrons.
• Electric charge (Coulomb) is a property of matter (positive, negative, neutral).
• Charge is conserved – it is never created or destroyed.
• Like charges repel, unlike charges attract.
• Charges arise from an imbalance of protons and electrons.
• Negative charge = more electrons than protons.
• Positive charge = more protons than electrons.
• Neutral charge = equal numbers of protons and electrons.
• Electrons move, protons do not.

Electrical Conductors and Insulators

• Electrical conductors allow electrons to move freely (e.g., metals like copper).
• Electrical insulators do not allow electrons to move freely (e.g., plastics, glass, silk).

Static Electricity

• Static electricity is the build-up of charge on an object.
• It can be built up in three ways: induction (no touching), conduction (touching), and friction.
• Induction involves inducing a charge on an object without touching it (creating an unbalanced charge).
• Conduction involves transferring charge between objects by touching them.
• Friction involves transferring charge when two objects move against each other.

Electrical Force

• Electrical force is the attraction or repulsion between two charged particles.
• It depends on the charge and the distance between the particles.

Electrical Fields

• An electrical field exists in the space around a charged particle.
• Field lines show the direction and strength of the field.
• Positive field lines point outward, negative inward.
• Electrical field lines never cross.

Current and Circuits

• Electrical potential energy depends on position in an electric field.
• Potential difference (voltage) is the change in electrical potential energy per unit charge.
• Voltage measures the difference in electrical potential between two terminals of a battery.
• Batteries are electrochemical cells converting chemical energy into electrical energy.
• Current (amperes) is the rate at which charges move through a wire.
• Direct current (DC) flows in one direction.
• Alternating current (AC) changes direction periodically.
• Resistance (ohms) opposes the flow of current due to internal friction; influenced by thickness, length, and temperature.
• Electrical conductors have low resistance; insulators have high resistance.
• Semiconductors have properties between conductors and insulators.
• Superconductors have zero resistance below a critical temperature.
• Ohm's Law: V = IR (Voltage = Current x Resistance)
• Circuits are paths for electron flow, including wires and a voltage source.
• Closed circuits allow current to flow, open circuits do not.
• Switches are used to control circuit flow.
• A schematic diagram is a diagram representing an electrical circuit.

Series and Parallel Circuits

• Series circuits have one path for electron flow, voltage is divided among components, and current is the same throughout.
  • A break in series circuit stops flow.
• Parallel circuits have multiple paths for electron flow, voltage is the same across each branch, and total current is the sum of currents in each branch.
  • A break in one path for parallel circuits does not stop the flow in others.

Electrical Power

• Electrical power (Watts) is the rate at which electrical energy is converted to other forms.
• P = IV = I²R = V²/R

Electromagnetism

• Electromagnetic force is a combination of electric and magnetic forces.
• Electromagnetic waves (like light) involve changing electric and magnetic fields.
• Solenoids are coils of wire that produce a magnetic field when current passes through them, increasing with more turns of the wire.
  • The right hand rule can determine the direction of the magnetic field.
• Electromagnets are rods of magnetic material surrounded by a solenoid, significantly increasing magnetic strength.
• Electric motors convert electrical energy into mechanical energy by interactions between magnetic fields created by currents and magnets.
• Electromagnetic induction is the process of producing a current in a circuit by changing a magnetic field.
  • Faraday's Law describes how a change in magnetic field can induce a current.
  • Changing magnetic fields around a loop of wires will induce a current; this depends on the relative degrees of the fields.

Transformers

• Transformers are devices that increase or decrease voltage.

Fuses and Circuit Breakers

• Fuses and circuit breakers protect circuits from excessive current.
  • Fuses are wires with low melting points; circuit breakers use magnets or bimetallic strips.
• Grounding safely transfers excess charge to the ground.

Magnetism

• Magnets have north and south poles; like poles repel, unlike poles attract.
• Impossible to isolate a single magnetic pole.
• Permanent magnets are always magnetized.
• Magnetic materials are influenced by magnetic fields, some permanently and some only temporarily.
• Magnetic fields are regions where magnetic force can be detected.