The so-called terminal voltage of a battery is lower than the emf when it is discharging because of the voltage drop across the internal resistance .
Why the terminal voltage potential difference is less than the emf of the cell?
When a cell is in closed circuit, i.e., when current is drawn from it, then the potential difference between its electrodes is called the terminal voltage. It is always less than the e.m.f. because when charge flows in a circuit, some energy is spent in the flow of charge through the electrolyte of the cell .
Can emf be less than terminal voltage?
Yes it can , for example when a cell is being recharged the terminal pd is V=E+IR where E is the emf of the cell, I is the current passing through the cell from positive to negative terminal and R is the internal resistance of the cell.
Is emf always positive in cells?
The maximum potential difference which can be measured for a given cell is called the electromotive force, abbreviated emf and represented by the symbol E. By convention, when a cell is written in shorthand notation, its emf is given a positive value if the cell reaction is spontaneous .
Can potential difference be greater than emf?
The potential difference across a battery cannot be greater than its emf . ... When current flows, the potential difference across the terminals of the battery is decreased as some potential drop due to its internal resistance.
What is the formula for electromotive force emf?
| varepsilon electromotive force | E the energy in the circuit | Q Charge of the circuit. |
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Can voltage be greater than emf?
They really test the internal resistance of the battery. ... The voltage output of the battery charger must be greater than the emf of the battery to reverse current through it . This will cause the terminal voltage of the battery to be greater than the emf, since V = emf − Ir, and I is now negative.
Is emf equal to voltage?
Electromotive force (EMF) is equal to the terminal potential difference when no current flows . EMF and terminal potential difference (V) are both measured in volts, however they are not the same thing. EMF (ε) is the amount of energy (E) provided by the battery to each coulomb of charge (Q) passing through.
What is standard emf of cell?
The cell potential is the difference between the electrode potentials (reduction potentials) of the cathode and anode. It is called the standard electromotive force (emf) of the cell when no current is drawn through the cells.
What is a positive emf?
Now, consider what is “positive EMF”? It is electromotive force which is in the same direction as that of the input current . On the other hand, the so-called “back EMF” to be induced according to the well-known Faraday’s law, is in the direction reverse to the input current. They are utterly different in nature.
What is the difference between E cell and emf?
| Nature of reaction | Equilibrium 0 0 | Non – spontaneous + – |
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Can the potential difference across the battery is greater than its emf?
So, the answer is when the battery is charging the potential difference can be greater than emf . Note: The voltage or electric potential difference across the terminals of a cell when no current is drawn from it.
What is emf in simple words?
Electromotive force , abbreviation E or emf, energy per unit electric charge that is imparted by an energy source, such as an electric generator or a battery. Energy is converted from one form to another in the generator or battery as the device does work on the electric charge being transferred within itself.
What is the formula of internal resistance?
Internal resistance is measured in Ohms. ... The relationship between internal resistance (r) and emf (e) of cell s given by. e = I (r + R) Where, e = EMF i.e. electromotive force (Volts), I = current (A), R = Load resistance, and r is the internal resistance of cell measured in ohms.
What is SI unit of emf?
Notation and units of measurement
Like other measures of energy per charge, emf uses the SI unit volt , which is equivalent to a joule per coulomb.
How do you calculate the emf?
The emf is equal to the work done on the charge per unit charge (ε=dWdq) when there is no current flowing . Since the unit for work is the joule and the unit for charge is the coulomb, the unit for emf is the volt (1V=1J/C).
