Two wires $A$ and $B$ made of same material and having their lengths in the ratio $6 : 1$ are connected in series. The potential difference across the wires are $3\,V$ and $2\,V$ respectively. If $r_A$ and $r_B$ are the radii of $A$ and $B$ respectively, then $\frac{{{r_B}}}{{{r_A}}}$ is
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A heater coil connected to a supply of a $220\, V$ is dissipating some power ${P_1}.$ The coil is cut into half and the two halves are connected in parallel. The heater now dissipates a power ${P_2}.$ The ratio of power ${P_1}\,\,:\,\,{P_2}$ is
A $100\, W$ bulb $B_1$, and two $60\,W$ bulbs $B_2$ and $B_3$, are connected to a $250\, V$ source, as shown in the figure. Now $ W_1, W_2$ and $W_3$ are the output powers of the bulbs $B_1, B_2$ and $B_3$, respectively. Then
In a large building, there are $15$ bulbs of $40\ W$, $5$ bulbs of $100\ W, 5$ fans of $80\ W$ and $1$ heater of $1\ kW$. The voltage of electric mains is $220\ V$. The minimum capacity of the main fuse of the building will be ................ $A$
In a neon discharge tube $2.9 \times {10^{18}}\,N{e^ + }$ ions move to the right each second while $1.2 \times {10^{18}}$ electrons move to the left per second. Electron charge is $1.6 \times {10^{ - 19}}\,C$. The current in the discharge tube
A $25\, watt$, $220\, volt$ bulb and a $100\, watt$, $220\, volt$ bulb are connected in parallel across a $220\, volt$ line. Which bulb will glow more brightly
$n$ identical cells each of $e.m.f.$ $E$ and internal resistance $r$ are connected in series. An external resistance $R$ is connected in series to this combination. The current through $R$ is
The resistance ofeach arm of the Wheatstone's bridge is $10\; ohm$. A resistance of $10 \;ohm$ is connected in series with a galvanometer then the equivalent resistance across the battery will be