Electric Circuits and Resistance

Electric Circuits

• A path through which electric current flows from a power source, through one or more devices, and back to the power source
• Consists of:
  • Power source (e.g. battery)
  • Conductors (e.g. wires)
  • Load (e.g. light bulb)
  • Switch (optional)

Resistance

• Opposition to the flow of electric current
• Measured in ohms (Ω)
• Depends on:
  • Material of the conductor
  • Length of the conductor
  • Cross-sectional area of the conductor
  • Temperature of the conductor
• Formula: R = ρ * L / A, where ρ is the resistivity of the material

Series Circuits

• Circuits in which components are connected one after the other
• Characteristics:
  • Current is the same throughout the circuit
  • Voltage is divided among the components
  • If one component fails, the entire circuit is broken
• Formulae:
  • Total resistance: R_total = R1 + R2 + ... + Rn
  • Total voltage: V_total = V1 + V2 + ... + Vn

Parallel Circuits

• Circuits in which components are connected between the same two points
• Characteristics:
  • Voltage is the same across each component
  • Current is divided among the components
  • If one component fails, the other components remain unaffected
• Formulae:
  • Total resistance: 1/R_total = 1/R1 + 1/R2 + ... + 1/Rn
  • Total current: I_total = I1 + I2 + ... + In

Energy Transfer

• The process of transferring energy from one place to another through electric circuits
• Types of energy transfer:
  • Electrical energy → light energy (e.g. light bulb)
  • Electrical energy → thermal energy (e.g. heater)
  • Electrical energy → kinetic energy (e.g. motor)
• Efficiency: ratio of useful output energy to input energy

Electric Circuits

• Electric current flows from a power source, through devices, and back to the power source
• Consists of a power source, conductors, load, and an optional switch

Resistance

• Opposition to electric current flow, measured in ohms (Ω)
• Depends on conductor material, length, cross-sectional area, and temperature
• Formula: R = ρ * L / A, where ρ is the resistivity of the material

Series Circuits

• Components are connected one after the other
• Characteristics: same current throughout, voltage divided among components, and single component failure breaks the entire circuit
• Formulae: Total resistance: R_total = R1 + R2 +...+ Rn, Total voltage: V_total = V1 + V2 +...+ Vn

Parallel Circuits

• Components are connected between the same two points
• Characteristics: same voltage across each component, current divided among components, and single component failure doesn't affect other components
• Formulae: Total resistance: 1/R_total = 1/R1 + 1/R2 +...+ 1/Rn, Total current: I_total = I1 + I2 +...+ In

Energy Transfer

• Process of transferring energy from one place to another through electric circuits
• Types of energy transfer: electrical energy → light, thermal, or kinetic energy
• Efficiency: ratio of useful output energy to input energy