Current-Potential Difference Graph for a Filament Lamp

Understanding the Current-Potential Difference Graph for a Filament Lamp

  • Definition of Key Terms:

    • Current (I): The flow of electric charge, measured in amperes (A).
    • Potential Difference (V): The difference in electric potential energy per unit charge, measured in volts (V).

  • Ohmic Conductors:

    • Resistors where current is directly proportional to potential difference (Ohm's Law): I∝VI \propto V.
    • Resistance (R) remains constant as long as temperature remains unchanged.

  • Filament Lamps:

    • Filament lamps contain a very fine wire (the filament), which glows when current flows through it due to heat generated.
    • Common example: household bulbs, torch bulbs.
    • The filament is coiled tightly, increasing its heating effect when current passes through.

  • Experiment Setup:

    • Replace a standard resistor with a filament lamp in the circuit to analyze the current-potential difference relationship.
    • Measure the current as the potential difference is increased.

  • Graph Analysis:

    • The resulting graph shows the relationship between current and potential difference for the filament lamp:
    • Initially, as potential difference increases, current increases but not at a constant rate.
    • Key Observation: As the temperature of the filament rises, its resistance also increases, leading to a decreasing rate of current with increasing potential difference.
    • Therefore, the filament lamp does not follow Ohm's law; it is not an ohmic conductor.

  • Temperature Effects:

    • Higher temperatures lead to greater atomic vibrations in the filament, causing more frequent collisions with electrons, resulting in increased resistance.
    • This is indicated graphically as a curve rather than a straight line, highlighting the non-linear relationship.

  • Examination Tips:

    • Understand the significance of the graph shape; it is commonly featured in exam questions.
    • Revise the differences between ohmic and non-ohmic conductors, specifically focusing on the filament lamp behavior in circuits.

  • Further Resources:

    • For additional practice and understanding, review the provided revision workbook linked in the video.