A horizontal wire carries 160 A current below which another wire of linear density $10 \mathrm{~g} / \mathrm{m}$ carrying a current is kept at 4 cm distance. If the wire kept below hangs in air, what is the current in this wire, when the direction of current in both the wires is same? $\left(g=10 \mathrm{~m} / \mathrm{s}^2\right.$ and $\left.\mu_0=4 \pi \times 10^{-7}\right)$
A long solenoid has 70 turns / cm and carries current $I$. An electron moves within the solenoid in a circle of radius 2.5 cm perpendicular to the solenoid axis. If the speed of the electron is $4.4 \times 10^6 \mathrm{~m} / \mathrm{s}$, then the current $I$ in the solenoid is
(take $\mu_0=4 \pi \times 10^{-7}$ Si unit, mass electron $=9 \times 10^{-31}$
kg , charge of electron $1.6 \times 10^{-19} \mathrm{C}$ )
A flat circular coil has 100 turns of wire of radius 10 cm . A uniform magnetic field exists in a direction perpendicular to the plane of the coil and it grows at a rate of $0.1 \mathrm{~T} / \mathrm{s}$. The induced emf in the coil is
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