In the following Wheatstone bridge $P/Q = R/S$. If key $K$ is closed, then the galvanometer will show deflection
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(d) Pressing the key does not disturb current in all resistances as the bridge is balanced. Therefore, deflection in the galvanometer in whatever direction it was, will stay.
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Resistance $n$, each of $r\; ohm$, when connected in parallel give an equivalentresistance of $R\; ohm$. If these resistances were connected in series, the combination would have a resistance in $ohms$, equal to
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 $r$.
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For current entering at $A$, the electric field at a distance '$r$'
from $A$ is
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