College Physics I – Introduction

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Emf

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College Physics I – Introduction

Definition

Electromotive force (emf) is the energy provided per unit charge by an energy source, such as a battery or generator. It is measured in volts and represents the potential difference that drives current around a circuit.

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5 Must Know Facts For Your Next Test

  1. Emf is not a force but a potential difference measured in volts.
  2. In a closed loop, the sum of emf sources equals the sum of voltage drops according to Kirchhoff’s Voltage Law.
  3. Emf sources can be both ideal and real; real sources have internal resistance.
  4. The symbol for emf in equations is usually $\mathcal{E}$ or $E$.
  5. A higher emf means more energy per charge is available to do work in the circuit.

Review Questions

  • What does electromotive force (emf) measure and in what units?
  • How does Kirchhoff’s Voltage Law relate to emf in a closed loop?
  • What is the significance of internal resistance in real emf sources?
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