wht's the basic deffrence b/w emf and current??????/and y we use emf while we could use current source i.e battery

EMF (Electromotive Force) and Current are two entirely different quantities
According to the definitions

EMF - Electromotive force or potential of a body is the work done in joules to bring a unit electric charge from infinity to the body

For a given device, if a charge Q passes across that device, and gains an energy U, the net emf for that device is the energy gained per unit charge, or U/Q. This has units of volts (V), or newton-meter/coulomb (N-m/C), and hence can be thought of as a voltage induced by the device in question

whereas

Current is the flow of charge (electrons in a conductor or ions in an electrolyte)

so we can see that EMF is a measure of energy per unit charge
and current is of course not a measure of energy it's in itself an energy

The second part of your question becomes invalid according to the above explanation as current cannot be an alternate to emf

I hope it makes some sense

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