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A platinum resistance thermometer has a resistance of $50\,\Omega $ at $20\,^o C$. When dipped in a liquid the resistance becomes $76.8\,\Omega $. The temperature coefficient of resistance for platinum is $\alpha = 3.92 \times {10^{ - 3}}\,^o C$. The temperature of the liquid is .............. $^o C$
Equal potentials are applied on an iron and copper wire of same length. In order to have the same current flow in the two wires, the ratio $r$ (iron)/$r$ (copper) of their radii must be (Given that specific resistance of iron = $1.0 \times {10^{ - 7}}$ $ ohm-m$ and specific resistance of copper = $1.7 \times {10^{ - 8}}\,ohm-m$)
Wheatstone bridge principle is used to measure the specific resistance $\left(S_1\right)$ of given wire, having length $L$, radius $r$. If $X$ is the resistance of wire, then specific resistance is: $S_1=X\left(\frac{\pi r^2}{L}\right)$. If the length of the wire gets doubled then the value of specific resistance will be :
A series combination of two resistors $1\,\Omega $ each is connected to a $12\,V$ battery of internal resistance $0.4\,\Omega $. The current flowing through it will be ............... $A$
The resistance of a bulb filmanet is $100\,\Omega$ at a temperature of $100\,^o C$. If its temperature coefficient of resistance be $0.005$ per $^o C$, its resistance will become $200\,\Omega$ at a temperature of ................ $^oC$
In the Wheatstone's bridge shown, $P = 2\,\Omega ,$ $Q = 3\,\Omega ,$ $R = 6\,\Omega $ and $S = 8\,\Omega $. In order to obtain balance, shunt resistance across '$S$' must be .............. $\Omega$