A current $I$ is passing through a wire having two sections $P$ and $Q$ of uniform diameters $d$ and $d/2$ respectively. If the mean drift velocity of electrons in sections $P$ and $Q$ is denoted by $v_P$ and $v_Q$ respectively, then
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Two wires of resistance $R_1$ and $R_2$ have temperature coefficient of resistance ${\alpha _1\,}{\rm{ and \,}}{\alpha _2}$, respectively. These are joined in series. The effective temperature coefficient of resistance is
This question has Statement $1$ and Statement $2.$ Of the four choices given after the Statements, choose the one that best describes the two Statements.
Statement $1 :$ The possibility of an electric bulb fusing is higher at the time of switching $ON.$
Statement $2:$ Resistance of an electric bulb when it is not lit up is much smaller than when it is lit up.
The resistivity of a potentiometer wire is $40 \times {10^{ - 8}}\,ohm - m$ and its area of cross-section is $8 \times {10^{ - 6}}\,{m^2}$. If $0.2\, amp$ current is flowing through the wire, the potential gradient will be
$3$ identical bulbs are connected in series and these together dissipate a power $P$. If now the bulbs are connected in parallel, then the power dissipated will be
A set of $n$ equal resistors, of value $R$ each, are connected in series to a battery of emf $E$ and internal resistance $R.$ The current drawn is $I.$ Now, the $n$ resistors are connected in parallel to the same battery. Then the current drawn from battery becomes $10\,I.$ The value of $n$ is
A milliammeter of range $10\, mA$ and resistance $9\, \Omega$ is joined in a circuit as shown. The meter gives full-scale deflection for current $I$ when $A$ and $B$ are used as its terminals, i.e., current enters at $A$ and leaves at $B$ ($C$ is left isolated). The value of $I$ is
When a resistance of $2\,ohm$ is connected across the terminals of a cell, the current is $0.5$ amperes. When the resistance is increased to $5\, ohm$, the current is $0.25\, amperes$. The internal resistance of the cell is ............. $ohm$