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
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A current of $1.6\, A$ is flowing through a wire having cross-sectional area $1\, mm^2$. If density of free electrons in the material of the wire is $10^{29}\, per\, m^3$, the drift velocity of electrons will be
A copper wire of length $10\,m$ and radius $\left(10^{-2} / \sqrt{\pi}\right) m$ has electrical resistance of $10 \,\Omega$. The current density in the wire for an electric field strength of $10( V / m )$ is :
One $kg$ of water, at $20\,^oC$, is heated in an electric kettle whose heating element has a mean (temperature averaged) resistance of $20\, \Omega $. The rms voltage in the mains is $200\, V$. Ignoring heat loss from the kettle, time taken for water to evaporate fully, is close to.......... $\min$ [Specific heat of water $= 4200\, J/kg\, ^oC$), Latent heat of water $= 2260\, k\,J/kg$]
A wire of length $10 \mathrm{~cm}$ and radius $\sqrt{7} \times 10^{-4} \mathrm{~m}$ connected across the right gap of a meter bridge. When a resistance of $4.5 \ \Omega$ is connected on the left gap by using a resistance box, the balance length is found to be at $60 \mathrm{~cm}$ from the left end. If the resistivity of the wire is $\mathrm{R} \times 10^{-7} \Omega \mathrm{m}$, then value of $\mathrm{R}$ is :