There is a current of $40$ ampere in a wire of ${10^{ - 6}}\,{m^2}$ area of cross-section. If the number of free electron per ${m^3}$ is ${10^{29}}$, then the drift velocity will be
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In the electric network shown, when no current flows through the $4\, \Omega $ resistor in the arm $EB$, the potential difference between the points $A$ and $D$ will be ............... $V$
Infinite number of cells having $emf$ and internal resistance $\left( {E,r} \right)$, $\left( {\frac{E}{n},\frac{r}{n}} \right)$, $\left( {\frac{E}{{{n^2}}},\frac{r}{{{n^2}}}} \right)$, $\left( {\frac{E}{{{n^3}}},\frac{r}{{{n^3}}}} \right)$..... are connected in series in same manner across an external resistance of $\frac{{nr}}{{n + 1}}$ . Current flowing through the external resistor is
A potentiometer circuit shown in the figure is set up to measure $e.m.f.$ of a cell $E$. As the point $P$ moves from $X$ to $Y$ the galvanometer $G$ shows deflection always in one direction, but the deflection decreases continuously until $Y$ is reached. In order to obtain balance point between $X$ and $Y$ it is necessary to
A thermocouple of negligible resistance produces an $e.m.f.$ of $40\,\mu V{/^o}C$ in the linear range of temperature. A galvanometer of resistance $10\; ohm$ whose sensitivity is $1\;\mu A/div$, is employed with the thermocouple. The smallest value of temperature difference that can be detected by the system will be
In the circuit shown, a four wire potentiometer is made of a $400\, cm$ long wire, which extends between $A$ and $B$. The resistance per unit length of the potentiometer wire is $r = 0.01\, \Omega /cm$. If an ideal voltmeter is connected as shown with jockey $J$ at $50\, cm$ from end $A$, the expected reading of the voltmeter will be: ............... $V$
A uniform metallic wire of length $L$ is mounted in two configurations. In configuration $1$ (triangle), it is an equilateral triangle and a voltage $V$ is applied to corners $A$ and $B$. In configuration $2$ (circle), it is bent in the form of a circle and the potential $V$ is applied at diametrically opposite points $P$ and $Q$. The ratio of the power dissipated in configuration $1$ to configuration $2$ is
For a wire $\frac{R}{l}=\frac{1}{2}$ and length of wire is $l=5\, cm .$ If potential difference $1\, V$ is applied across it, current through wire will be: $( R =$ Resistance $)$ (in $A$)