Question

EMF and Terminal Voltage

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Answer 1

Answer:

Explanation:

 

Electromotive Force:

EMF of a cell or battery is the total voltage or potential difference developed between the two terminals of the cell/battery when the two terminals are in open circuit condition. Or. the EMF of a cell/battery is the potential difference built between the two terminals of the cell/battery when no current is being drawn from it.  To measure the EMF of a cell/battery we can simply connect a voltmeter two the two terminals of the cell or battery.

EMF of a cell depends upon the physical and electrical properties of the electrodes and electrolytes used to build the cell and EMF of a battery depends upon the EMF of the cell , numbers of cells and the cells combination types used to build the battery.

Terminal Voltage:

Terminal Voltage of a cell or battery is the potential difference build between the two terminals of the cell/battery or load when a load is connected to the cell or battery or when a current is being drawn from the cell or battery. Due to the internal resistance of a cell/battery some EMF is used to overcome the resistance so the terminal voltage of a cell or battery is always smaller than it’s EMF . The terminal voltage of a cell/battery depends on the EMF of the cell/battery , Internal resistance and the load resistance.

The difference between and EMF ( EMF)  and Terminal Voltage ( V) of a cell/battery can be calculated as following:

EMF - V = I \times r

Where, I is the total current being drawn from the cell/battery and r is the internal resistance of the cell/battery.

Internal resistance:

Due to various physical and chemical constraints the electron when travelling from the negative terminal of a cell or battery to the positive terminal , experiences some resistance. This resistance experienced by an electron or current inside the cell or battery is called the internal resistance of the cell or battery. Such resistance is caused due to resistance of electrodes , deposition or extra materials in electrolytes and electrodes of a cell. Is the Internal resistance of a cell or battery which resists the flow of electron through the cell/battery and causes the Terminal Voltage to be smaller than the actual EMF of the cell/battery.

The current delivered ( I ) to a load ( R) from a cell with internal resistance (r) can be calculated as:

I =$\dfrac{EMF}{R+r} = \dfrac{E}{R+r}$

And the Potential difference across the load or the Terminal Voltage can be calculated as:

V = I.R =$\dfrac{E}{R+r}$times R

hope it helps

Answer 2

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The electromotive force (emf) is the potential difference of a source when no current is flowing. Terminal voltage is the voltage output of a device is measured across its terminals. Terminal voltage is calculated by V = emf - Ir.

It is represented by “ε” and the measuring unit is same as voltage i.e. Volt. EMF is the maximum potential difference between two points of the battery when no current is flowing from the source in case of open circuit. In short, EMF is the cause and Voltage or potential difference is the effect.