The emf of a battery is equal to its terminal potential difference. A. Under all

Question

The emf of a battery is equal to its terminal potential difference. A. Under all conditions B. Only where a large current is in the battery C. Only when there is current in the battery D. Only when the battery is being charged E. Under no condition. Let Q demote charge, V denote potential difference and U denote stored energy of their quantities, in parallel must have the same A. O only B. O and V only c. Q and U only d. U only E. v only The capacitance of a parallel-plate capacitor on be increased by A. Increasing the charge B. Decreasing the charge C. Decreasing the plate area D. Increasing the plate separation

Explanation / Answer

(1)

e= V_t- ir

The potential difference between the terminals of a battery will equal the emf of the battery when there is no current in the battery. At this time, the current though, and hence the potential drop across the internal resistance is zero. This only happens when there is no load placed on the battery—that includes measuring the potential difference with a voltmeter! The terminal voltage will exceed the emf of the battery when current is driven backward through the battery, in at its positive terminal and out at its negative terminal.

(2)

V only

(3)

C= eo A/d

decreasing plate separation

(4)

U = Q^2/2C

U' = Q^2/ 2 ( 2C)

= 8/2

= 4 J

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