c (c) Length is immaterial for an electric fuse wire.
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A meta sample carrying a current along $x-$ axis with density $J$ is subjected to a magnetic field $B$ (along $z-$ axis). The electric field $E$ developed along $y-$ axis is directly proportional to $J$ as well as $B$. The constant of proportionality has $SI\ unit$
For a cell, the graph between the potential difference $(V) $ across the terminals of the cell and the current $(I)$ drawn from the cell is shown in the figure. The $e.m.f.$ and the internal resistance of the cell are
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.......
$n$ 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 : $(n > 4)$
The charge flowing through a resistance $R$ varies with time $t$ as $ Q=at-bt^2 $ where $a$ and $b$ are positive constants . The total heat produced in $R$ is
A copper wire has a square cross-section, $2.0\, mm$ on a side. It carries a current of $8\, A$ and the density of free electrons is $8 \times {10^{28}}\,{m^{ - 3}}$. The drift speed of electrons is equal to
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 ............... $\mathrm{V}$