Beginner's qt on emf

[rahuld.exe]

'it is emf when no current is flowing outside the cell. Whereas, it is potential difference is when current actually flows out of the cell."

"that emf is the potential difference when there is no current flowing through the circuit or when the key is open. Whereas, the circuit has certain value of potential difference when there is current flowing through the circuit."

i read it somewhere n i guess both mean the same.... can someone please explain what, how, when, why (basically, everything about it)... in case they dont mean the same thing kindly explain both...
regards

 

[rick_741]

The electromotive force is the theoretical maximum value for the potential difference the battery can maintain, based on how it was built.

When you connect the battery to a closed circuit, inside the battery is triggered a chemical reaction that sustain this potential difference. There are ions inside the battery that must move constantly, providing the electrons to go around the circuit. The problem is, this movement of the ions is not instantaneous and electrons are not readily available. This time for the electrons to become available acts somewhat like an internal resistance of the battery. Since the current of ions inside the battery have this internal resistance they must overcome, it reduces the actual potential difference that the battery can maintain when it is connected to a circuit.

 

[rahuld.exe]

hmm.. that helped.. thanks!