Terminal Potential Difference in Circuits

Terminal Potential Difference (p.d.)

• Terminal potential difference (p.d.) is the voltage measured across the terminals of a cell.
• In the absence of internal resistance, terminal p.d. equals the electromotive force (e.m.f.) of the cell.
• Due to internal resistance, terminal p.d. is always less than the e.m.f.
• When a load resistor (R) is connected across the terminals, the terminal p.d. is equivalent to the voltage across the load resistor.

Key Equations

• Terminal p.d. Equation:
  • VR = I × R
  • Where VR = terminal p.d. (V), R = load resistance (Ω), I = current (A).
• Lost Volts Equation:
  • Vr = I × r
  • Where Vr = lost volts (V), r = internal resistance (Ω), I = current (A).

Internal Resistance and Lost Volts

• When current flows through the cell, a potential difference develops across the internal resistance.
• This voltage (lost volts) is not available for the circuit and represents energy lost in the cell.

Potential Difference vs. Electromotive Force

• Potential difference describes energy loss of charges as they pass through a resistive component, converting electrical energy into heat.
• Electromotive force (e.m.f.) indicates energy transfer from the power source to electrical charges in the circuit.

Conceptual Understanding

• Potential difference illustrates the conversion of electrical energy to other forms, highlighting energy loss.
• E.m.f. signifies the energy supplied to the charge carriers by the cell, before they encounter any resistance in the circuit.

This quiz explores terminal potential difference (p.d.) and its relationship with electromotive force (e.m.f.) in electrical circuits. It covers key equations related to terminal p.d., lost volts, and the effects of internal resistance. Assess your understanding of these fundamental concepts in electricity!