Understanding Electricity and Atoms

Understanding Electricity

• Electricity powers technology including cell phones, computers, lights, and air conditioning.
• Defined as the flow of electric charge, it manifests in various forms throughout nature.
• Key questions about electricity involve the origin, movement, and effects of electric charges.

Building Blocks of Atoms

• An atom consists of three particles: electrons, protons, and neutrons.
• Protons and neutrons are densely packed in the nucleus, surrounded by orbiting electrons.

Protons

• Each atom contains at least one proton which determines the atomic number.
• The number of protons identifies the chemical element (e.g., 1 proton = Hydrogen, 29 protons = Copper).
• In a balanced atom, the number of protons equals the number of electrons.
• Protons always carry a positive charge.

Electrons

• Electrons are crucial for electricity and carry a negative charge.
• Valence electrons are located in the outer orbit and can escape, becoming free electrons.
• Free electrons are essential for allowing charge movement.

Neutrons

• Neutrons exist alongside protons in the nucleus and provide stability by preventing proton repulsion.
• Neutrons are neutral, carrying no charge, and determine the isotope of an atom.

Electrostatic Force (Coulomb’s Law)

• Attraction exists between the nucleus and electrons, aiding electron flow.
• Opposite charges attract while like charges repel, which is fundamental to electric charge behavior.

Conductivity

• Conductivity indicates how tightly bound an electron is to its atom.
• Conductors (e.g., metals like copper and silver) have high conductivity due to mobile electrons, allowing electron flow and are often malleable.

Insulators

• Insulators are non-metals with low conductivity, preventing electron flow (e.g., glass, rubber).

Semiconductors

• Semiconductors are semi-metals that conduct electricity but break when struck (e.g., boron, silicon).
• They may provide a dull glow when electricity flows through them.

Current

• Current (I) refers to the flow rate of electrons in a circuit, measured in Amperes.
• 1 Ampere equals 1 Coulomb per second, with 1 Coulomb representing approximately 6.24 x 10^18 electrons.
• Andre-Marie Ampere is a notable figure in electromagnetism, contributing significantly to its foundational principles.

Current Flow Conventions

• Electron Current: Electrons flow from negative to positive potential (low to high).
• Conventional Current: Benjamin Franklin proposed that positive charge flows from high to low potential (positive to negative).

Voltage

• Represents electric potential energy stored in a circuit, indicating how much energy can perform work when released.
• Measured in Joules (J); 1 Joule is the energy transferred when a force of 1 Newton moves an object a distance of 1 meter.

Electric Potential

• The electric potential at a point is the electric potential energy per unit charge, expressed in Joules per Coulomb (V).
• For instance, 10 Volts means one Coulomb can do 10 Joules of work moving from a higher to a lower potential.

Voltage Properties

• Also known as Potential Difference or EMF; it acts as electrical pressure that drives electrons through a circuit.
• Alessandro Volta invented the first chemical battery and is an important figure in the study of voltage.

Resistance

• Resistance opposes current flow, generating heat, and limits electron flow in circuits.
• Measured in Ohms (Ω); a resistance of 1Ω occurs when 1 Volt pushes 1 Ampere of current.

Factors Affecting Resistance

• Material: Silver has the lowest resistance, followed by copper and aluminum.
• Cross-sectional area: Smaller areas increase resistance, while larger areas decrease it.
• Length: Longer conductors result in higher resistance.
• Temperature: Increased temperature leads to higher resistance; cooler wires have lower resistance.

Georg Ohm

• A German physicist who established that voltage and current are directly proportional, contributing to Ohm's Law.

Resistor

• Resistors are passive components that limit electrical current flow in circuits, denoting their inability to generate power.
• Types:
  • Through-hole (PTH): Feature long leads for insertion into breadboards or PCBs.
  • Surface-mount: Compact, soldered directly onto PCBs, enhancing mass circuit board protection.

Decoding Resistor Markings

• Resistor bands indicate significant digits, weight for multiplication, and tolerance.
• Color Code:
  • Black: 0 (x1)
  • Brown: 1 (x10)
  • Red: 2 (x100)
  • Orange: 3 (x1000)
  • Yellow: 4 (x10,000)
  • Green: 5 (x100,000)
  • Blue: 6 (x1,000,000)