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Two wires $A$ and $B$ of the same material, having radii in the ratio $1: 2$ carry currents in the ratio $4: 1$. The ratio of drift speed of electrons in $A$ and $B$ is
A railway compartment is lit up by thirteen lamps each taking $2.1\, amp$ at $15\, volts$. The heat generated per second in each lamp will be ............ $cal$
In the circuit as shown in the figure, the heat produced by $6\, ohm$ resistance due to current flowing in it is $60$ calorie per second. The heat generated across $3\, ohm$ resistance per second will be ................. $calorie$
A $220 \; V , 50 \; Hz$ AC source is connected to a $25 \; V$, $5 \; W$ lamp and an additional resistance $R$ in series (as shown in figure) to run the lamp at its peak brightness, then the value of $R$ (in ohm) will be
$50\,\Omega $ and $100\,\Omega $ resistors are connected in series. This connection is connected with a battery of $2.4\, volts$. When a voltmeter of $100\,\Omega $ resistance is connected across $100\,\Omega $ resistor, then the reading of the voltmeter will be ............. $V$
The resistances of the platinum wire of a platinum resistance thermometer at the ice point and steam point are $8 \Omega$ and $10 \Omega$ respectively. After inserting in a hot bath of temperature $400^{\circ} \mathrm{C}$, the resistance of platinum wire is: