Resistance

• Potential difference (V) = current (A) x resistance (Ohms)
• V = IR
• Voltmeter V reads 6 V and resistor R is 4 ohms. What is the current through ammeter A?

  1.5 A
• Ohmic conductors have a constant resistance
• At constant temperatures, the current flowing through an ohmic conductor is directly proportional to the potential difference across it (V=IR)
• The resistance of some resistors and components does change (filament lamp or a diode)
• The electrical charge to the filament lamp transfers to the thermal energy store to heat up. resistance increases with temperature, as current increases the temperature of the filament lamp increases and the resistance increases
• For diodes, the resistance depends on the direction of the current, lets current flow in one direction but have high resistance if its reversed
• Ohmic conductors have a constant resistance at a constant temperature
• When temperature changes, the resistance of the component changes (except for thermistors)