EMF and Potential

Visualize the fundamental difference between Electromotive Force (EMF) and Potential Difference (PD) in real-time. Click on components to interact and see how EMF and PD behave differently!

⚡

EMF: The Battery's Push

Energy supplied by the battery per unit charge. It's the cause of current flow. Present even when circuit is open.

🔌

PD: Energy Used by Components

Energy used per unit charge across circuit components. It's the effect of EMF. Only present when current flows.

Controls

Electromotive Force (EMF)

Circuit Open - EMF Present

Definition: Energy supplied by the battery per unit charge (the "cause" of current flow).

Key Point: EMF exists even when the circuit is open. It's the battery's total voltage.

EMF Formula:
EMF (ε) = Vterminal + I × r

Potential Difference (PD)

Definition: Energy used per unit charge across circuit components (the "effect" of EMF).

Key Point: PD only exists when current flows. It's the voltage drop across components.

PD Formula:
PD (V) = I × R

EMF vs PD Comparison

⚡ EMF
  • Energy PROVIDED by source
  • CAUSE of current flow
  • Constant for ideal source
  • Present even when circuit is OFF
  • Measured across source terminals with no load
  • Maximum possible voltage
🔌 PD
  • Energy USED by components
  • EFFECT of current flow
  • Depends on circuit conditions
  • Only present when current flows
  • Measured across components when circuit is ON
  • Always less than or equal to EMF

Circuit Visualization

Click on components to interact
EMF (ε)
1.50V
Battery's total voltage
PD (V)
0.00V
Across bulb
Current (I)
0.00A
Caused by EMF
Power (P)
0.00W
P = V × I
EMF - The battery's pushing force (Cause)
PD - Voltage drop across components (Effect)