EMF Calculator
Calculate EMF, terminal voltage, and cell combinations for electrochemical cells and batteries. Includes Nernst equation for non-standard conditions and series/parallel cell calculations. Essential for CBSE Class 12 and JEE Physics and Chemistry.
EMF Calculator
Terminal Voltage (V)
11 V
V = E − Ir = 12 − 2 × 0.5 = 11 V
Voltage Drop (Ir)
1 V
Power Delivered
22 W
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V = terminal voltage, E = EMF, I = current, r = internal resistance, n = number of cells/electrons, Q = reaction quotient
Frequently Asked Questions
What is EMF (Electromotive Force)?
EMF is the potential difference across the terminals of a cell when no current is flowing (open circuit). It represents the total energy per unit charge supplied by the cell. EMF is measured in volts (V). The formula relating EMF to terminal voltage is: V = E − Ir, where E is EMF, I is current, and r is internal resistance.
What is the difference between EMF and terminal voltage?
EMF (E) is the total voltage the cell can provide with no load. Terminal voltage (V) is the actual voltage across the terminals when current flows. Terminal voltage is always less than EMF because some voltage is lost across the internal resistance: V = E − Ir. This is a key concept in CBSE Class 12 and JEE Physics.
What is the Nernst equation?
The Nernst equation calculates the EMF of an electrochemical cell under non-standard conditions: E = E° − (RT/nF) ln(Q), or at 25°C: E = E° − (0.0592/n) log(Q). Here E° is the standard EMF, n is the number of electrons transferred, and Q is the reaction quotient. This is important for CBSE Class 12 Chemistry and JEE.
How do cells combine in series and parallel?
In series: total EMF = sum of individual EMFs, total internal resistance = sum of individual internal resistances. In parallel (identical cells): total EMF = EMF of one cell, total internal resistance = r/n (where n is number of cells). Series gives higher voltage; parallel gives higher current capacity.