Lecture on Potential Difference

Objectives

• Explain what is meant by potential difference
• Describe how to measure potential difference
• Describe potential difference in series circuits

Key Concepts

Electric Current

• Electric current is a flow of electrons around a circuit.
• In a simple circuit: electrons move out of the cell, pass through the wire, through the lamp, and return to the cell.
• The lamp lights up because electrons transfer energy to it.

Energy Transfers in a Circuit

• The cell contains chemical energy, converted to electrical energy, carried by electrons.
• As electrons pass through components (e.g., lamp), electrical energy is transferred to other forms:
  • Light energy
  • Thermal energy

Potential Difference (Voltage)

• Potential difference, also known as voltage, indicates energy transfer in a circuit.
• 1 volt = 1 joule of energy transferred per coulomb of charge.
• Measured using a voltmeter.

Measuring Potential Difference

• Voltmeter symbol is important to learn.
• Measure potential difference by placing voltmeter across the component.
• Example: A cell with a potential difference of 9 volts indicates electrons transfer 9 joules of energy per coulomb of charge.

Potential Difference in Series Circuits

Single Lamp Circuit

• The potential difference across the lamp matches the cell.
• All electrical energy is transferred to the lamp as light and thermal energy.

Series Circuit with Two Lamps

• Total potential difference across the cell remains the same (e.g., 9 volts).
• Each lamp has a potential difference of 4.5 volts.
• Energy is shared between lamps, making them dimmer than a single lamp circuit.

Non-identical Lamps in Series

• Example: One lamp at 6 volts, another at 3 volts.
• Total potential difference across both lamps equals the cell's potential difference.
• Lamp at 6 volts is brighter, transferring more energy than the 3-volt lamp.

Recap

• The cell's potential difference determines energy transfer per coulomb of charge.
• In series circuits, energy is shared, affecting brightness based on individual potential differences.
• Practicing series circuit problems can be done using provided workbooks.