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$n$ identical cells are joined in series with two cells $A$ and $B$ with reversed polarities. $emf$ of each cell is $E$ and internal resistance is $r$. Potential difference across cell $A$ and $B$ is : $(n > 4)$
In the adjacent shown circuit, a voltmeter of internal resistance $R$, when connected across $B$ and $C$ reads $\frac{{100}}{3}\,V$. Neglecting the internal resistance of the battery, the value of $R$ is ................. $k \Omega$
The actual value of resistance $R$, shown in the figure is $30\,\Omega $. This is measured in an experiment as shown using the standard formula $R = \frac{V}{I}$ where $V$ and $I$ are the readings of the voltmeter and ammeter, respectively. If the measured value of $R$ is $5\%$ less, then the internal resistance of the voltmeter is ................. $\Omega$
An electron (charge $= 1.6 × 10^{-19}$ coulomb) is moving in a circle of radius $5.1 × 10^{-11}\,m$ at a frequency of $6.8 × 10^{15} $ revolutions/sec. The equivalent current is approximately
In $a$ wire of cross-section radius $r$, free electrons travel with drift velocity $v$ when a current $I$ flows through the wire. What is the current in another wire of half the radius and of the same material when the drift velocity is $2v$?
A potentiometer wire of length $10 \,m$ and resistance$20 \,\Omega$ is connected in series with a $25 \,V$ battery and an external resistance $30\, \Omega$. A cell of emf $E$ in secondary circuit is balanced by $250\, cm$ long potentiometer wire. The value of $E$ (in volt) is $\frac{x}{10}$. The value of $x$ is.......
In the given figure $-1$, resistance of shown voltmeter is variable. Variation of whose reading with respect to its resistance is shown in figure $-2$. The value of $R$ is ............... $\Omega$
In a metre-bridge when a resistance in the left gap is $2\ \Omega$ and unknown resistance in the right gap, the balance length is found to be $40\ \mathrm{~cm}$. On shunting the unknown resistance with $2\ \Omega$, the balance length changes by :