A $10\,m$ long potentiometer wire has a potential gradient of $0.0025\, V/cm$. Calculate the distance of null point when the wire is connected to a $1.025\,V$ standard cell ............... $\mathrm{m}$
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$n$ equal cell having emf $E$ and internal resistance $r$, are connected in a circuit of a resistance $R$ . Same current flows in circuit either they are connected in series or parallel, if
$AB$ is a potentiometer wire of length $100\, cm$ and its resistance is $10 \,\Omega$. It is connected in series with a resistance $R = 40 \,\Omega$ and a battery of $e.m.f.$ $2 \,V$ and negligible internal resistance. If a source of unknown $e.m.f.$ $E$ is balanced by $40\, cm$ length of the potentiometer wire, the value of $E$ is ................. $V$
A cell of $emf$ $E$ and internal resistance $r$ is connected in series with an external resistacne $nr.$ Then, the ratio of the terminal potential difference to $emf$ is
Two rods of copper and iron with the same cross-sectional area are joined at $S$ and a steady current $I$ flows through the rods as shown in the figure. Choose the most appropriate representation of charges accumulated near the junction $S$.
In order to determine the $e.m.f.$ of a storage battery it was connected in series with a standard cell in a certain circuit and a current $I_1$ was obtained. When the battery is connected to the same circuit opposite to the standard cell a current $I_2$ flow in the external circuit from the positive pole of the storage battery was obtained. What is the $e.m.f$. $\varepsilon_1$ of the storage battery? The $e.m.f$. of the standard cell is $\varepsilon_2$.
Three equal resistors connected in series across a source of $e.m.f.$ together dissipate $10\, watt$. If the same resistors are connected in parallel across the same $e.m.f.$, then the power dissipated will be .............. $watt$
Voltmeter reads potential difference across the terminals of an old battery as $1.2\,volt$ , while a potentiometer reads $1.4\,volt$ . The internal resistance of battery is $40\,\Omega $ , then voltmeter resistance is .............. $\Omega$