28. Magnetic Fields and Forces

Which option best completes the following sentence? If a magnet is carefully balanced, as in a compass, the north end of the magnet points roughly toward…

A wire carries a positive current to the left in the plane of this screen. What is the direction of the magnetic field at a point near the top of the screen, still in the plane of the screen?

At what distance from a wire carrying a 10 Acurrent is the magnetic field strength equal to $50\mu \mathrm{T}$? This is the approximate value of the earth's magnetic field.

Two long parallel wires lie in the $xy$-plane, each carrying a $5.0$ A current in opposite directions. Wire 1 lies along the$y=3.0\mathrm{ cm}$ line and carries a current in the positive $x$-direction; wire 2 lies along the $y=0$ line and carries a current in the negative $x$-direction. What is the magnitude of the magnetic field at the point $\left(0\text{cm,}1\text{.5}\text{cm,}0\mathrm{ cm}\right)$?