How can you differentiate between emf and potential difference? What do you mean by emf? Is it really a force? Explain

Difference Between EMF and Potential Difference

Aspect Electromotive Force (EMF) Potential Difference (PD)
Definition The total energy supplied by a source per unit charge to drive the charge around a complete circuit. The energy difference per unit charge between two points in a circuit.
Symbol ε V
Formula ε= V=W/Q
Source Produced by a cell, battery, or generator. Occurs across circuit components (e.g., resistor, capacitor).
Cause Due to chemical, mechanical, or magnetic energy conversion. Due to charge movement in a circuit.
Circuit Condition Present even when no current flows (open circuit). Exists only when current flows.
Unit Volt (V) Volt (V)

Definition of Electromotive Force (EMF)

Electromotive Force (EMF, denoted as ε) is the energy supplied by a source per unit charge to move it around a complete circuit. It is the driving force that pushes electrons and establishes an electric current.

Mathematically:

ε=W/Q

where:

  • ε = EMF (in volts, V)
  • W = Work done or energy supplied (in joules, J)
  • Q = Charge (in coulombs, C)

Is EMF Really a Force?

No, EMF is not a force in the mechanical sense.

  • Despite its name, EMF is not a physical force but rather a potential energy per unit charge.
  • It is called “force” because it acts as a driving agent for electric charge movement.
  • The term originated historically when scientists initially thought it was a force.

In summary, EMF is a voltage that drives electric current, and it is different from potential difference because it is the total energy supplied by a source, while PD refers to energy lost or used within a circuit.

Related Questions:

  1. If aluminum and copper wires of the same length have the same resistance, which has the larger diameter? Why?
  2. Two electric bulbs marked 100 W, 220 V and 200 W, 220 V have tungsten filaments of the same length. Which bulb has a thicker filament?
  3. Show that Volt-Ampere is equal to Watt (SI unit of power).
  4. Define and explain the term electric current. What is the difference between electronic current and conventional current?
  5. Can current flow through a circuit without potential difference? Explain.
  6. Can current flow through a circuit without potential difference? Explain.
  7. What is the resistance across an open switch and a closed switch of a circuit?
  8. Why is a bird sitting on a high-voltage transmission line not electrocuted? Why does it get electrocuted when it touches another wire?
  9. 5. How can you arrange five resistances to form a circuit with resistance smaller than any given resistance?
  10. 6. You are given wires, each with resistance . What is the ratio of maximum to minimum resistance that can be obtained?
  11. Why are we advised not to touch electrical switches with wet hands?
  12. Why is it dangerous to touch a live wire while standing barefoot on the earth?
  13. One of a car’s headlamps is burnt, but the second lamp is still working. What does this indicate about the connection?
  14. Physics 10 MCQ
  15. Simple harmonic motion and waves
  16. Simple harmonic motion and waves-NFE
  17. Give an example of vibratory motion which is not simple harmonic motion. Give a reason for your selection.
  18. At the extreme position, velocity is zero but acceleration is maximum in simple harmonic motion. How can you theoretically explain it?
  19. What will happen to the acceleration of a mass-spring system if its mass is doubled?
  20. A simple pendulum has a time period “T”. What will happen to its time period if its thread length is shortened to half?