A wire of length $10 \mathrm{~cm}$ and radius $\sqrt{7} \times 10^{-4} \mathrm{~m}$ connected across the right gap of a meter bridge. When a resistance of $4.5 \ \Omega$ is connected on the left gap by using a resistance box, the balance length is found to be at $60 \mathrm{~cm}$ from the left end. If the resistivity of the wire is $\mathrm{R} \times 10^{-7} \Omega \mathrm{m}$, then value of $\mathrm{R}$ is :
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Two bulbs $X$ and $Y$ having same voltage rating and of power $40\, watt$ and $60\, watt$ respectively are connected in series across a potential difference of $300\, volt$, then
When the resistance $R$ (indicated in the figure below) is changed from $1 \,k \Omega$. to $10 \,k \Omega$, the current flowing through the resistance $R'$ does not change. What is the value of the resistor $R'?$
In a potentiometer arrangement, a cell of $emf$ $1.25\; V$ gives a balance point at $35.0\; cm$ length of the wire. If the cell is replaced by another cell and the balance point shifts to $63.0\; cm ,$ what is the $emf$ of the second cell in $V$?
In the circuit shown in the figure, the switch $S$ is initially open and the capacitor is initially uncharged. $ I_1, I_2$ and $I_3$ represent the current in the resistance $2\,\Omega , 4\,\Omega $ and $8\,\Omega$ respectively.
Two wires each of radius of cross section $r$ but of different materials are connected together end to end (in series). If the densities of charge carriers in the two wires are in the ratio $1 : 4$, the drift velocity of electrons in the two wires will be in the ratio:
A student is provided with a variable voltage source $V$, a test resistor $R_T=10\,\Omega$, two identical galvanometers $G_1$ and $G_2$ and two additional resistors, $R _1=10\,M\,\Omega$ and $R _2=0.001\,\Omega$. For conducting an experiment to verify ohms law, the most suitable circuit is: