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A potentiometer wire of length $100\, cm$ has a resistance of $10\,\Omega $. It is connected in series with a resistance and a cell of $emf$ $2\, V$ and of negligible internal resistance. A source of $emf$ $10\,mV$ is balanced against a length of $40\, cm$ of the potentiometer wire. What is the value of external resistance ? .................. $\Omega$
Two resistance of $100\ \Omega$ and $200\ \Omega$ are connected in series with a battery of $4 \mathrm{~V}$ and negligible internal resistance. $A$ voltmeter is used to measure voltage across $100 \Omega$ resistance, which gives reading as $1 \mathrm{~V}$. The resistance of voltmeter must be ___$\Omega$.
A generator has armature resistance of $0 .1\,\Omega $ and develops an induced emf of $120 \,V$ when driven at its rated speed. Its terminal voltage when a current of $50\,A$ is being drawn is ................. $V$
Three resistors are connected to form the sides of a triangle $ABC$, the resistance of the sides $AB$, $BC$ and $CA$ are $40\,ohms$, $60\,ohms$ and $100\,ohms$ respectively. The effective resistance between the points $A$ and $B$ in $ohms$ will be
There are $0.8 \times 10^{23}$ free electrons $/ cm^3$ in copper. If $0.2\, A $ current is flowing is copper wire, then the drift velocity of electrons will be, if the cross sectional area of wire is $0.01 \,cm^2$
Under what condition current passing through the 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.