Electric Charge and Coulomb's Law

• Charge is the fundamental physical quantity for electrical phenomena, measured in Coulombs (C).
  • Positive charge (proton) is 1.6 × 10−19 C.
  • Negative charge (electron) is −1.6 × 10−19 C.
• Charging methods: rubbing, conduction, and induction.
• Conductors allow heat and electric charges to pass.
• Semiconductors perform both insulation and conduction.
• Insulators do not allow heat and electricity to pass.
• Net charge is the sum of all positive and negative charges; neutrons have zero net charge.
• The triboelectric series lists materials by their tendency to become positive or negative to predict static electricity.
• The law of conservation of charge states a system maintains charge equilibrium unless charge is added or removed.
• Coulomb’s Law describes electrostatic forces between charged particles.
• An electric field is the region where Coulomb force is experienced.
• Gauss’ Law relates electric field on a closed surface to the enclosed charge which quantifies electric field strength over an area.
• A Gaussian surface is a hypothetical surface immersed in an electric field that may enclose a charge.
• Electric flux measures the strength of an electric field over an area.

Electric Circuitry

• An equipotential surface is a region where all points have equal electric potential, represented by lines.
• Electric potential energy is potential energy from a moving charge’s displacement within an electric field.

Voltage

• Voltage is electric potential energy per unit charge, measured in volts.
• Potential difference is the difference between two electric potential values, producing electric current.
• Electron work is the loss of potential energy of a moving test charge in an electric field.
• Potential gradient is the local rate of change of potential with respect to displacement.
  • Positive charges accelerate down gradients.
  • Negative charges accelerate up gradients.
• A capacitor stores electrical charges.

Capacitance

• Capacitance is a capacitor's ability to store charge, changing voltage by one unit, measured in farads.
• Decreasing the area of parallel-plate capacitors reduces capacitance.
• Stored energy is energy stored due to half the work performed.
• Electric field energy is the energy of the electric field, equal to the electric field’s energy density.
• A dielectric is an insulating material between capacitor plates suitable for use include: ceramic, metal oxide, and plastic.
• Equivalent capacitance is the total capacitance within sets of capacitors in a circuit.
• In a series circuit, devices are connected in a single fashion, sharing charge values.

Electrical Safety Devices

• Shuttered sockets have internal shutters to prevent objects from being inserted.
• A fuse protects circuits from excessive current by melting and opening the circuit.
• A circuit breaker protects from current overload and can be reset, unlike fuses.
• A ground fault circuit interrupter (GFCI) detects current mismatches to prevent electrocution, required in areas with water.
• An equipotential earth point/stud ensures all equipment is grounded at the same low potential.
• A three-pronged plug provides a ground outlet to divert excess current to the ground.

Physiological Effects of Electric Shock

• Electrolysis causes ulceration due to polarized ions.
• Burns range from minor to serious injuries, caused by low-to-high voltages.
• Muscle cramps are uncontrollable twitching due to electrical overstimulation.
• Ventricular fibrillation is muscle cramps affecting the heart.

Definition of Terms

• Electric current is the amount of charge in a conductor per unit time.
• Current density is the amount of current per unit area.
• Drift velocity is the net motion of charged particles in groups.
• Resistance is the property of a material to resist current, measured in Ohms.
• Resistivity measures a material’s electrical resistance.
• Conductivity is the inverse of resistivity, measuring a material’s conductance.
• Ohm’s Law states current is directly proportional to voltage across a conductor with constant resistance.

Ohmic devices

• Ohmic devices follow Ohm’s Law, with constant resistance, examples include Anohmic device and Isohmic device.
• Non-Ohmic devices do not follow Ohm’s Law.
• Conductance is the inverse of resistance, measuring a material’s ability to conduct current, measured in siemens.
• Electrical energy is converted potential energy.
• Electric shock is physiological injury caused by electric current.
• Electrocution is death due to electric shock.

Kirchhoff’s Rules

• Current Law: At any junction, the sum of currents in equals the sum of currents out.
• Voltage Law: Voltage gain must equal voltage loss in a complete circuit loop.
• Electromotive force concerns work for a circuit's energy and isn't a force.

Fundamentals of Magnetism

• A magnet interacts with materials easily influenced by magnetism, named after Magnesia in ancient Greece.
• A magnetic pole is a region of a magnet that is polarized.
  • A magnetic monopole has one polarized end.
  • A magnetic dipole has two polarized ends.
• A magnetic field is the field of force surrounding a magnet.
  • A charged particle moving inside a magnetic field moves parallel to itself.
• Charges are dictated by the right-hand rule.
• Lorentz force is influenced by both electric and magnetic forces.
  • If magnetic force is stronger than velocity, a charged particle moves in a spiral.
• Cyclotron radius is the radius of a charged particle’s circular motion.
• Cyclotron frequency is the angular frequency of a charged particle’s circular motion.
• Magnetic flux measures magnetic field strength per area, measured in Weber.
• A solenoid is a conducting wire coiled in a helix, similar to arranged single-loop conductors.
• The Biot-Savart Law describes the magnetic field generated by changing electric fields.