Physics

• The higher the potential difference

  The higher the current
• The lower the resistance

  The higher the current
• Potential difference


  The voltage or electrical pressure that drives the flow of current
• Calculating Current

  V = potential difference

  R = resistance

  I = V/R
• Resistance


  Anything that opposes the current, making it more difficult to flow
• Potential difference


  Volts (V) in an electric circuit
• Current


  Amps (A)
• Calculating Resistance


  R=pd÷current
• Calculating Potential difference


  V=IR
• Ohm's law


  At constant temperature, the current through a component is directly proportional to the potential difference
• Ohm's law is represented by the symbol Ohms (Ω)
• As the length of were increases

  The resistance increases
• Ohmic conductor


  A component that allows current to flow through it easily and obeys ohmic law
• To connect an ohmic conductor

  1. Connect ammeter in series

  2. Connect voltmeter in parallel
• Ohmic law
• Filament lamp's resistance


  Does not remain constant
• Filament lamp

  • As the temperature increases, the resistance increases
  • It is more difficult for the current to flow
  • Current is not directly proportional to resistance
• National grid


  System of pylons, cables & transformers that transfers electrical power from power stations to people's homes
• Step-Up Transformers


  1. Increase potential difference (voltage)

  2. Decrease current

  3. Reduce energy losses through the cables (as thermal energy)
• Step-Down Transformers


  1. Reduce the potential difference

  2. To make potential difference safe for use in homes
• Direct proportion is when one variable increases so the other also increases.
• Inverse proportion is when one variable increases and the other decreases.
• The length of a wire is directly proportional to its resistance.
• Resistance is constant only if the temperature is constant.