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 $S$.
A
B
C
D
KVPY 2018, Diffcult
Download our app for free and get started
B
b $(b)$ When a current flows through a junction or a contact between two metals of different conductivities a charge is accumulated in the vicinity of contact. The charge accumulation is directly proportional to the current. Charge accumulation occurs in a region whose thickness is nearly equals to the mean free path in the metal.
In case current flows from a metal of large conductivity to a metal of small conductivity, charge accumulation is of positive type and vise-versa. So, correct option is $(b)$.
Download our app
and get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
$10\,Cells$, each of emf $'E'$ and internal resistance $'r'$, are connected in series to a variable external resistance. Figure shows the variation of terminal potential difference of their combination with the current drawn from the combination.$Emf$ of each cell is ............. $V$
In a potentiometer experiment two cells of $e.m.f.$ $E_1$ and $E_2$ are used in series and in conjunction and the balancing length is found to be $58\, cm$ of the wire. If the polarity of $E_2$ is reversed, then the balancing length becomes $29\, cm$. The ratio $\frac{{{E_1}}}{{{E_2}}}$ of the $e.m.f.$ of the two cells is
A resistance of $2 \Omega$ is comnected across one gap of a metre-bridge (the length of the wire is $100 \mathrm{~cm}$ ) and an unknown resistance, greater than $2 \Omega$, is connected across the other gap. When these resistance are interchanged, the balance point shifts by $20 \mathrm{~cm}$. Neglecting any corrections, the unknown resistance is
A hollow cylindrical conductor has length of $3.14\,m$, while its inner and outer diameters are $4\,mm$ and $8\,mm$ respectively. The resistance of the conductor is $n \times 10^{-3}\,\Omega$.If the resistivity of the material is $2.4 \times 10^{-8}\,\Omega\,m$. The value of $n$ is $..........$
As shown in the figure, a potentiometer wire of resistance $20\,\Omega$ and length $300\,cm$ is connected with resistance box (R.B.) and a standard cell of emf $4\,V$. For a resistance ' $R$ ' of resistance box introduced into the circuit, the null point for a cell of $20\,mV$ is found to be $60\,cm$. The value of ' $R$ ' is $.....\Omega$