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Question
Thu February 24, 2011 By: Annie Joseph

# why during discharging: Terminal p.d. V emf E. V = E+Ir?? why???why??

Tue March 01, 2011
Dear student,

Electromotive force is the voltage of your battery.
It is the MAXIMUM voltage the circuit can attain. So, when you place a voltmeter in parallel to your battery/cell, the reading shown is your Electromotive Force, or EMF.

Whereas, PD or potential difference is simply the difference of the voltage before and after experiencing a resistance effect. So basically, the potential difference can never be equal to the EMF in a circuit because there is always energy lost as heat, or some other form.

1) during discharge: terminal V < emf, due to the voltage drop from internal resistance
2) during recharge: terminal V > emf, due to restoration of potential difference across the terminals of the battery (i.e. voltage source)

Hope this helps.
Team
Topperlearnin g.com
Related Questions
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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