Question 6: What is the difference between emf and P.D?

ANSWER

Emf

P.D

(1) emf is the voltage across the terminals of a battery when it is not providing current to the circuit. (2) It is the energy provided by the source in moving a unit positive charge from negative to positive terminal and mathematically, emf = W/q where W is the work done on the charge. (3) ε = v +Ir where r is the internal resistance of the emf source. Therefore, emf is greater than the potential difference. (4) emf is produced by some chemical reaction in the source. (5) emf decreases with time.

(1) Potential difference is the difference in the potential of two points. (2) It is the work done per unit positive charge between two points in the electric field against the direction of electric field. Mathematically, ∆V = W_{AB}/q, where A and B are two points in the field and ∆V is P.D. (3) P.D is less than emf. V = ε –Ir, where I is current flowing in the circuit. (4) P.D is the difference in potential of two points. (5) P.D remains constant.

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