Ow is an electromagnet different from a bar magnet?

question 3 options:

a. only a bar magnet has a magnetic field.

b. only an electromagnet attracts materials made of iron.

c. an electromagnet is temporary and is magnetic when a current flows through a wire wrapped around the core.

d. a bar magnet is a temporary and is only magnetic when a current flows through a wire wrapped around the core.

Two resistors r1 and r2 may be connected either in series or parallel across an ideal battery with emf ε. we desire the rate of energy dissipation of the parallel combination to be 8.75 times that of the series combination. if r1 = 105 ω, what are the (a) smaller and (b) larger of the two values of r2 that result in that dissipation rate?

Athin nonconducting rod with a uniform distribution of positive charge q is bent into a circle of radius r. the central perpendicular axis through the ring is a z-axis, with the origin at the center of the ring. a) what is the magnitude of the electric field due to the rod at z = 0? n/c (b) what is the magnitude of the electric field due to the rod at z = infinity? n/c (c) in terms of r, at what positive value of z is that magnitude maximum? r (d) if r = 4.00 cm and q = 9.00 µc, what is the maximum magnitude? n/c

Acorporation gives out its profits as dividends paid to whom?