Why does a stationary electromagnet attached to an ac source induce current in a wire coil?

How does the kinetic energy of a charge change as the charge moves under the effect of an electric field from higher potential to lower potential? a.the kinetic energy increases.b.the kinetic energy decreases.c.the kinetic energy remains the same.d.the kinetic energy is always zero.

Abookcase has a mass of 38 kg and the coefficient of friction between it and the floor is 0.82 what is the maximum force of friction between the bookcase and the floor a 372n b 305n c 412n d 449n

Determine the moment of the force f about an axis extending between a and c. express the result as a cartesian vector. a is at the origin, c is at (4,3,0) and f = (4i + 12j -3k) lb coming out of b (4,3,-2).