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Two identical cells each of emf $1.5\,V$ are connected in series across a $10\,\Omega$ resistance. An ideal voltmeter connected across $10\,\Omega$ resistance reads $1.5\,V$. The internal resistance of each cell is $......\Omega$.
Under what conditions current passing through a resistance $R$ can be increased by short circuiting the battery of emf $E_2$. The internal resistances of the two batteries are $r_1$ and $r_2$ respectively
In the circuit shown the cells $A$ and $B$ have negligible resistance. For $V _{ A }=12\; V , R _{1}=500\; \Omega$ and $R =100\; \Omega$ the galvanometer $(G)$ shows no deflection. The value of $V_{B}$ is .... $V$
A current of $2\, mA$ was passed through an unknown resistor which dissipated a power of $4.4\, W$. Dissipated power when an ideal power supply of $11\, V$ is connected across it is
The resistance of hot tungsten filament is about $10$ times the cold resistance. What will be the resistance of $100\, W$ and $200\, V$ lamp when not in use ............. $\Omega $
Consider a block of conducting material ofresistivity '$\rho$' shown in the figure. Current '$I$' enters at '$A$' and leaves from '$D$'. We apply superp osition principle to find voltage '$\Delta V$ ' developed between '$B$' and '$C$'. The calculation is done in the following steps:
$(i)$ Take current '$I$' entering from '$A$' and assume it to spread over a hemispherical surface in the block.
$(ii)$ Calculatefield $E(r)$ at distance '$r$' from $A$ by using Ohm's law $E = \rho j$, where j is the current per unit area at '$r$'.
(iii) From the '$r$' dependence of $E(r)$, obtain the potential $V(r)$ at $r$.
(iv) Repeat $(i), (ii)$ and $(iii)$ for current '$I$' leaving '$D$' and superpose results for '$A$' and '$D$'.
$50\,\Omega $ and $100\,\Omega $ resistors are connected in series. This connection is connected with a battery of $2.4\, volts$. When a voltmeter of $100\,\Omega $ resistance is connected across $100\,\Omega $ resistor, then the reading of the voltmeter will be ............. $V$
A new flashlight cell of $e.m.f.$ $1.5\, volts$ gives a current of $15\, amps$, when connected directly to an ammeter of resistance $0.04\,\Omega $. The internal resistance of cell is ........... $\Omega$
There is a current of $20$ amperes in a copper wire of ${10^{ - 6}}$ square meter area of cross-section. If the number of free electrons per cubic meter is ${10^{29}}$, then the drift velocity is