In the adjoining circuit, the battery ${E_1}$ has an $e.m.f.$ of $12\,volt$ and zero internal resistance while the battery $E$ has an $e.m.f.$ of $2\,volt$. If the galvanometer $G$ reads zero, then the value of the resistance $X$ in $ohm$ is
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A copper wire of diameter $1.02\, mm$ carries a current of $1.7\, amp$. Find the drift velocity $(v_d)$ of electrons in the wire. Given $n$, number density of electrons in copper $= 8.5 \times 10^{27} /m^3$....................... $mm/sec$
Figure shows a thick shell made of electrical conductivity $\sigma$ and has inner & outer radii of $10\ cm$ & $20\ cm$ respectively and is filled with ice inside it. Its inside and outside surface are kept at different potentials by a battery of internal resistance $\frac{2}{\pi} \Omega \ \&\ \in = 5V$. Find value of $\sigma$ for which ice melts at maximum possible rate if $25\%$ of heat generated by shell due to joule heating is used to melt ice.
A $10 \,m$ long potentiometer wire is connected to a battery having a steady voltage. A Leclanche cell is balanced at $4 \,m$ length of the wire. If the length is kept the same, but its cross-section is doubled, the null point will be obtained at ........... $m$
Two cells, $e.m.f.$ of each is $E$ and internal resistance $r$ are connected in parallel between the resistance $R$. The maximum energy given to the resistor will be, only when
Figure shows three similar lamps $L_1, L_2$ and $L_3$ connected across a power supply. If the lamp $L_3$ fuses, how will the light emitted by $L_1$ and $L_2$ change ?
A uniform wire of length $l$ and radius $r$ has a resistance of $100\, \Omega $. It is recast into a wire of radius $\frac{r}{2}$. The resistance of new wire will be ............... $\Omega$
Four ammeters with identical internal resistances $r$ and a resistor of resistance $R$ are connected to a current source as shown in figure. It is known that the reading of the ammeter $A_1$ is $I_1 = 3\ A$ and the reading of the ammeter $A_2$ is $I_2 = 5\ A$ . Determine the ratio of the resistances $R/r$ .