When a current of $2\, A$ flows in a battery from negative to positive terminal, the potential difference across it is $12\, V$. If a current of $3\, A$ flows in the opposite direction potential difference across the terminals of the battery is $15\, V$, the $emf$ of the battery is ............... $\mathrm{V}$
A$12.6$
B$13.2$
C$13.5$
D$14$
Medium
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B$13.2$
b $\mathrm{T} . \mathrm{P.D.}=\mathrm{E}-\mathrm{I} \mathrm{r} \Rightarrow 12=\mathrm{E}-2 \mathrm{r}$ ..........$(1)$
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In a typical Wheatstone network, the resistances in cyclic order are $A = 10 \,\Omega $, $B = 5 \,\Omega $, $C = 4 \,\Omega $ and $D = 4 \,\Omega $ for the bridge to be balanced
Three $60\, W$ light bulbs are mistakenly wired in series and connected to a $120\,V$ power supply. Assume the light bulbs are rated for single connection to $120\,V$. With the mistaken connection, the power dissipated by each bulb is: .................. $W$
Assertion $(A):$ In a meter bridge experiment, null point for an unknown resistance is put inside an enclosure maintained at a higher temperature. The null point can be obtained at the same $p$ as before by decreasing the value of the standard resistance.
Reason $(R):$ Resistance of metal increases with increase in temperature.
With a potentiometer null point were obtained at $140\, cm$ and $180\, cm$ with cells of $emf$ $1.1 \,V$ and one unknown $X\, volts$. Unknown $emf$ is .............. $V$