2.1.5 Resistors

• Resistor

  A component used to resist the flow of electric current in a circuit
• Functions of Resistors

  • Current Limiting
  • Voltage Division
  • Biasing
  • Load Resistors
• Current Limiting protects components by limiting the current to safe levels
• Voltage Division creates a voltage drop used in voltage dividers
• Biasing sets the operating point of other electronic components, like transistors
• Load Resistors are used to simulate a load in circuits for testing purposes
• Ohm’s Law

  Relates voltage (V), current (I), and resistance (R) in a circuit: V=I×R
• Calculating Resistance

  Rearranging Ohm’s Law to find resistance: R=V/I
• Types of Resistors

  • Fixed Resistors
  • Variable Resistors
  • Specialized Resistors
• Fixed Resistors

  Have a constant resistance value
• Fixed Resistors

  • Carbon film resistors
  • Metal oxide resistors
• Variable Resistors

  Allow adjustment of resistance value
• Variable Resistors

  • Potentiometer
  • Rheostat
• Specialized Resistors

  Designed for specific applications
• Specialized Resistors

  • Thermistors
  • Light Dependent Resistors (LDRs)
• Resistors are color-coded to indicate their resistance value and tolerance
• Color Code Chart

  • First two bands represent significant digits
  • Third band is a multiplier
  • Fourth band indicates tolerance
• Brown (1), Black (0): 10
• Red (multiplier of 10^2): 100
• Golden (tolerance of ±5%)
• The resistor value is 10×100=1000 Ω or 1 kΩ with a tolerance of ±5%
• Series Resistors

  • Connected end-to-end
  • Total resistance is the sum of individual resistances
  • Same current through all resistors
  • Total voltage is the sum of the voltages across each resistor
• Parallel Resistors

  • Connected across the same two points
  • Total resistance is the reciprocal of the sum of reciprocals of individual resistances
  • Current is divided among the resistors
  • Same voltage across each resistor
• Power Dissipation

  The rate at which energy is converted into heat by a resistor
• Resistors are rated for maximum power they can safely dissipate
• Exceeding the power rating can damage the resistor and cause overheating
• Practical Applications of Resistors

  • Current Limiting
  • Voltage Dividers
  • Pull-Up and Pull-Down Resistors
• Practical Experiments with Resistors

  • Measuring Resistance
  • Building Circuits
  • Exploring Ohm’s Law
• Use a multimeter to measure the resistance of different resistors and compare with their color-coded values
• Connect resistors in series and measure the total resistance and voltage drop across each resistor
• Connect resistors in parallel and measure the total resistance and current through each branch
• Vary the voltage across a resistor and measure the current to verify Ohm’s Law
• Resistors limit current and adjust voltage in a circuit
• Use V=I×R to calculate voltage, current, or resistance
• Decode resistance values using color bands
• Understand how resistance behaves differently in series and parallel configurations
• Ensure resistors are used within their power rating to avoid damage