Question
Sun July 24, 2011 By: Hardik Gupta

# What actually is emf and what is that makes emf differ from potential difference?

Sun July 24, 2011
EMF or electro motive force is measured by the amount of work done in moving a unit positive charge in the complete circuit inside and outside the cell but potential difference is the amount of work done in moving a unit positive charge in the circuit outside the cell.
EMF is a characteristic of the cell i.e., it does not depend on the amount of current drawn from the cell but potential difference depends on the amount of current drawn from the cell. More the current is drawn from the cell, less is the potential difference.
EMF is equal to the potential difference when cell is not in use, while greater than the terminal voltage when cell is in use whereas potential difference is equal to the emf when the cell is not in use and less than the emf when the cell is in use.
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Wed January 18, 2017

# A cell of emf E and internal resistance r is connected to two external resistance R1 and R2 and a perfect ammeter.The current in the circuit is measured in four different situation: (i)without any external resistance in the circuit (ii)with resistance R1 only (iii)with Ri and R2 in series combination (iv)with R1 and R2 in parallel combination The currents measured in the four cases are 0.42A,1.05A,1.4A and 4.2A,but not necessarily in that order.Identify the currents corresponding to the four cases mentioned above.

Thu November 24, 2016

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