Question

Write the difference between potential difference and emf.

Answer 1

EMF:

$\to$ Work done by a source in taking a unit charge once around complete circuit.

$\to$ EMF exists even when ckt is open

$\to$ EMF is independent of external resistance

$\to$ EMF transforms energy from non electrical form to electrical form

P.D:

$\to$ Work done in moving a charge from one point to another point.

$\to$ P.D. exists only when ckt is closed

$\to$ P.D depends on resistance b/w $2$ points & current flowing through it

$\to$ P.D is the actual output voltage across battery.

(i) E$=$EMF

V$=(p-1)$

$(E-1r)=v$ discharge

$(E-ir)=iR$

$i=\frac{E}{(R+r)}$

$v=iR=\frac{ER}{R+r}$.

(ii) $v-R-ir=0$

$v=E+ir$

chargings

(iii) $v=E$ no internal loss.