A current of $2\,A$ flows through a wire of crosssectional area $25.0\,mm ^2$. The number of free electrons in a cubic meter are $2.0 \times 10^{28}$. The drift velocity of the electrons is $...............\times 10^{-6}\,ms ^{-1}$ (given, charge on electron $=1.6 \times 10^{-19}\,C$ )
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In a potentiometer wire experiment the $\mathrm{emf}$ of a battery in the primary circuit is $20\,V$ and its internal resistance is $5\,\Omega$ . There is a resistance box in series with the battery and the potentiometer wire, whose resistance can be varied from $120\,\Omega$ to $170\,\Omega$ . Resistance of the potentiometer wire is $75\,\Omega$ . The following potential differences can be measured using this potentiometer.
The resistance of the filament of a lamp increases with the increase in temperature. A lamp rated $100\, W, 220\, V$ is connected across $220\, V$ power supply. If the voltage drops by $10\%$ then the power of lamp will be
Two electric bulbs marked $40\,W,$ $220\,V$ and $60\,W,\,\,220\,V$ when connected in series across same voltage supply of $220\,V,$ the effective power is $P_1$ and when connected in parallel, the effective power is $P_2.$ Then $\frac {P_1}{P_2}$ is
The electric current through a wire varies with time as $I=I_0+\beta t$. where $I_0=20 \mathrm{~A}$ and $\beta=3 \mathrm{~A} / \mathrm{s}$. The amount of electric charge crossed through a section of the wire in $20 \mathrm{~s}$ is :
A resistance wire connected in the left gap of a meter bridge balances a $10\, \Omega$ resistance in the right gap at a point which divides the bridge wire in the ratio $3: 2 .$ If the length of the resistance wire is $1.5 m ,$ then the length of $1\, \Omega$ of the resistance wire is $....... \times 10^{-2}\;m$
The length of a potentiometer wire is $\ell $. A cell of emf $E$ is balanced at a length $\ell /3$ from the positive end of the wire. If the length of the wire is increased by $\ell /2$ at what distance will the same cell give a balanced point
To measure the temperature coefficient of resistivity $\alpha$ of a semiconductor, an electrical arrangement shown in the figure is prepared. The arm BC is made up of the semiconductor. The experiment is being conducted at $25^{\circ} \mathrm{C}$ and resistance of the semiconductor arm is $3 \mathrm{~m} \Omega$. Arm BC is cooled at a constant rate of $2^{\circ} \mathrm{C} / \mathrm{s}$. If the galvanometer $\mathrm{G}$ shows no deflection after $10 \mathrm{~s}$, then $\alpha$ is :