Circuits

• Parallel circuits are used in domestic settings because you can switch off each bulb individually, and the brightness of the bulbs dont change when you add more to the circuit
• The current in a series circuit depends on the applied voltage to the components, and the number and nature of said components
• Ohm's Law


  I = V/R (Current is directly proportional to voltage when resistance is constant)
• As voltage increases


  Current increases proportionally
• Resistors


  Current follows Ohm's Law (Current through a resistor increases linearly with the voltage applied across it)
• Metal filament lamps


  • Show a non-linear relationship between current and voltage
  • As voltage increases, resistance of the filament increases due to heating, causing the current to increase at a decreasing rate
• Diodes


  • Only allow current to flow in one direction
  • Current-voltage relationship is non-linear
  • When forward-biased, they conduct current
  • When reverse-biased, they block current flow
• Investigating current-voltage relationships experimentally

  1. Set up circuits with different components

  2. Measure current and voltage using a multimeter

  3. Change the voltage across the components and measure the corresponding currents

  4. Plot graphs to observe how current varies with voltage for each component
• If you increase the resistance in a circuit, the current will decrease. This is because as resistance goes up, it restricts the flow of current. It's like trying to push water through a narrower pipe - the flow will slow down.

  On the flip side, if you decrease the resistance in a circuit, the current will increase. Lower resistance allows more current to flow, similar to opening up a wider pipe for water to flow through.

  So, changing the resistance in a circuit directly affects the current - more resistance, less current; less resistance, more current.
• LDRs produce resistance in response to light, e.g the brighter the light, the lower the resistance and vice versa
• Thermistors produce resistance in response to temperature, e.g the higher the temperature, the lower the resistance and vice versa
• Lamps and LEDs can be used to indicate the presence on a current