In a potentiometer circuit a cell of $EMF$ $1.5\, {V}$ gives balance point at $36\, {cm}$ length of wire. If another cell of $EMF$ $2.5\, {V}$ replaces the first cell, then at what length of the wire, the balance point occurs ? (in $cm$)
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A wire of resistor $R$ is bent into a circular ring of radius $r$. Equivalent resistance between two points $X$ and $Y$ on its circumference, when angle $XOY$ is $\alpha$, can be given by
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 $2v$ ?
An infinite sequence of resistance is shown in the figure. The resultant resistance between $A$ and $B$ will be, when ${R_1} = 1\,ohm$ and ${R_2} = 2\,ohm$ ............. $\Omega$
A heating coil can heat the water of a vessel from $20\,^oC$ to $60\,^oC$ in $30$ minutes. Two such heating coils are put in series and then used to heat the same amount of water through the same temperature range. The time taken now will be ............ $min$ (neglecting thermal capacity of the coils)
A cell of internal resistance $3\, ohm$ and $emf$ $10\, volt$ is connected to a uniform wire of length $500 \,cm$ and resistance $3\, ohm$. The potential gradient in the wire is .............. $mV/cm$
A potentiometer having the potential gradient of $2\, mV/cm$ is used to measure the difference of potential across a resistance of $10 \,\Omega$. If a length of $50\, cm$ of the potentiometer wire is required to get the null point, the current passing through the $10 \,\Omega$ resistor is (in $mA$)