Lan tries to make a 10 W lightbulb light up by connecting it to a battery with an insulated copper wire. When the lightbulb does not light up, she assumes
that the battery is dead. What can she do to make an electric current flow
through the lightbulb?
A. Replace the battery with a coil of the wire, and then pass a magnet
back and forth through the coil.
B. Replace the battery with a magnet, and then pass a piece of wire
back and forth over the magnet.
O C. Wrap a magnet with several coils of the wire, and then hold the
lightbulb close to the wire.
D. Wrap the lightbulb with several coils of the wire, and then hold a
magnet close to the wire.

Consider a uniformly charged ring in the xy plane, centered at the origin. the ring has radius a and positive charge qdistributed evenly along its circumference. a)what is the direction of the electric field at any point on the z axis? . b)what is the magnitude of the electric field along the positive z axis? use k in your answer, where k=14πϵ0. d)the ball will oscillate along the z axis between z=d and z=−d in simple harmonic motion. what will be the angular frequency ω of these oscillations? use the approximation d≪a to simplify your calculation; that is, assume that d2+a2≈a2. express your answer in terms of given charges, dimensions, and constants