An infinitely long solenoid of radius r0 centered at the origin, which produces a time-dependent magnetic field απr02 cos(ωt) (where α and ω are constants), is placed along the z-axis. A circular loop of radius R, which carries a unit line charge density, is placed, initially at rest, on the xy-plane with its center on the z-axis. If R > r0, the magnitude of the angular momentum of the loop is:

A long rectangular metallic loop of width W and length L (L ≫ W) starts entering a region where there is a uniform magnetic field B perpendicular to the plane of the loop. The resistance of the loop is R and its mass is M. If v0 is the velocity of the loop just before entering the region, then neglecting self-inductance effects, the velocity at a later time t is:

Electromagnetic waves of frequency ω are incident on an electron gas whose relaxation time is τ. Let σlow and σhigh represent the respective electrical conductivities of the gas in low frequency (ωτ ≪ 1) and high frequency (ωτ ≫ 1) limits. The ratio (σlow / σhigh) is: