Potential Difference

• A cell makes one end of the circuit positive and the other negative. This sets up a?potential difference?across the circuit
• The potential difference across a component in a circuit is defined as;

energy transferred per unit charge

• The energy is transferred is from electrical energy into other forms, depending on the component or device being used
• Potential difference is measured in?volts (V)?which are equivalent to?Joule per coulomb (J C?1)
• The potential difference of a power supply connected in series is always shared between all the components in the circuit

The potential difference is the voltage across each component in a circuit

• Another description of energy transfer is?work done
• Therefore, potential difference can also be defined as the?work done per unit charge

Potential difference is the work done per unit charge

Measuring Potential Difference

• ?Potential difference or voltage is measured using a?voltmeter
  • A voltmeter is always set up in parallel to the component being measured

Potential difference can be measured by connecting a voltmeter in parallel between two points in a circuit

Conductor Length

• The equation for?resistivity?is

• 
• ?Where:
  • R?= resistance (Ω)
  • ρ?= resistivity (Ω m?1)
  • l?= length (m)
  • A?= area (m?2)

• Therefore, as the length of a uniform conductor at constant temperature increases, resistance also increases
• Voltage and current are linked by?Ohm's Law
• 
• Where
  • V?= potential difference (V)
  • I?= current (A)
  • R?= resistance (Ω)
• Therefore, as?R?increases, so must potential difference across the wire
  • Potential difference increases uniformly with length