Sound is generated by the speaker cone vibrating in different ways. The cone vibrates as different magnetic forces act on the current-carrying coil. Why do the magnetic forces acting on the coil change as the current running through the coil changes?

Charge is distributed along the entire x-axis with uniform density λ. how much work does the electric field of this charge distribution do on an electron that moves along the y-axis from y = a to y = b? (use the following as necessary: a, b, ε0, λ, and q for the charge on an electron.)