A) \[2.03\,\,V\]
B) \[2.54\,\,V\]
C) \[1.25\,\,V\]
D) \[1.39\,\,V\]
Correct Answer: D
Solution :
The emf of a cell is defined as work done by the cell in moving unit positive charge in the whole circuit including the cell once. Therefore, if \[W\] is the work done by a cell in moving charge\[q\] once around a circuit including the cell, then \[emf\,\,E=\frac{W}{q}\] or \[E=\frac{W}{it}\] Given,\[i=2\,\,A,\,\,t=6\min =6\times 60\,\,s,\,\,W=1000\,\,J\] Hence, \[E=\frac{1000}{2\times 6\times 60}=1.39\,\,V\] Note: The term emf (electromotive force) is misleading introduced by volta who thought it to be force that causes the current to flow. Actually emf is not a force but work required to carry unit charge from lower potential to higher potential inside the cell.
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