Forty electric bulbs are connected in series across a $220\, V$ supply. After one bulb is fused, the remaining $39$ are connected again in series across the same supply. The illumination will be
AMore with $40$ bulbs than with $39$
BMore with $39$ bulbs than with $40$
C
Equal in both the cases
DIn the ratio of ${49^2}:{39^2}$
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BMore with $39$ bulbs than with $40$
b (b) When $1$ bulb fuses, the total resistance of the circuit decreases hence the current increases. Since $P = {i^2}R$, therefore illumination increases.
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In the figure shown for gives values of $R_1$ and $R_2$ the balance point for Jockey is at $40\,cm$ from $A$. When $R_2$ is shunted by a resistance of $10\, \Omega$ , balance shifts to $50\,cm.$ $R_1$ and $R_2$ are $(AB = 1 \,m)$
A circuit of resistacne $R$ is connected to $n$ similar cells. If the current in the circuit is the same when the cells are connected in series or in parallel. If the internal resistacne $r$ of each cell then
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 '$D$'.
For current entering at $A$, the electric field at a distance '$r$'
from $A$ is
$A$ Wheatstone's bridge is balanced with a resistance of $625\, \Omega$ in the third arm, where $P, Q$ and $S$ are in the $1^{st}, 2^{nd}$ and $4^{th}$ arm respectively. If $P$ and $Q$ are interchanged, the resistance in the third arm has to be increased by $51\,\Omega$ to secure balance. The unknown resistance in the fourth arm is ............. $\Omega$
Three resistances of magnitude $2$, $3$ and $5$ $ohm$ are connected in parallel to a battery of $10\, volts$ and of negligible resistance. The potential difference across $3\,\Omega $ resistance will be ............... $volts$
The potential difference across the $100\,\Omega$ resistance in the following circuit is measured by a voltmeter of $900 \,\Omega$ resistance. The percentage error made in reading the potential difference is
By which of the following single load resistance the load bridge should be replaced so that the power to the load remains unchanged ................ $\Omega$
Figure shows a cross-section of a large-section of an infinite metal sheet carrying an electric current along its surface. The current per unit length is $J$ . A current carrying square loop is placed nearby the metal sheet such that the plane of square is perpendicular to the plane of sheet then