Resistors

• If the resistance is constant, an ohmic conductor, current is directly proportional to the potential difference.
• Ohmic Conductor

  Current is directly proportional to the p.d. in an ohmic conductor at a constant temperature. The resistance is constant.

  
• Filament Lamp

  As more current flows through the filament, its temperature increases. The atoms in the wire vibrate more, and collide more often with electrons flowing through it, so resistance increases as temperature increases. The resistance of a thermistor decreases and temperature increases. The resistance of a light dependent resistor (LDR) decreases as light intensity increases.

  
• Diode

  The current through a diode only flows in one direction – called the forward direction. There needs to be a minimum voltage before any current will flow.

  
• What happens if you add a resistor parallel to an existing resistor?

  Resistance decreases