28. Magnetic Fields and Forces

Which of the following factors can affect the strength of a magnetic field produced by a current-carrying wire?

Which of the following best describes a magnetic field?

A current-carrying circular coil lies flat in the $xy$-plane with current flowing counterclockwise when viewed from above. In which direction does the magnetic field at the center of the coil point?

When a magnet spins near a conducting wire, does the changing magnetic field create an electric field that causes electrons to move in the wire?

Two long, straight, parallel wires carry currents in the same direction. What is the direction of the magnetic field produced by wire $2$ at the location of wire $1$?

A long straight current-carrying wire runs vertically upward. At point $z$, which is located to the east of the wire, what is the direction of the magnetic field produced by the wire at that point?

Which of the following statements about the direction of the $B$ field (magnetic field) around a straight, current-carrying wire is correct?

Which of the following is the primary source of magnetic fields $B$?

In devices that use electromagnets, why is a permanent magnet often included as well?

Which of the following components are typically found in the magnetic system of a magneto?

How can magnets attract or repel each other without touching?

In the context of Earth's magnetic field, what is one end of a magnetized compass's needle attracted to?

In a typical bar magnet, where is the magnetic force the strongest?

If you bring the $\mathrm{north} \mathrm{pole}$ of one bar magnet close to the $\mathrm{north} \mathrm{pole}$ of another bar magnet, will these magnets be attracted or repelled?

A bar magnet is placed near the end of a solenoid with its north pole facing the solenoid's south pole. When current flows through the solenoid to create a south magnetic pole at the end closest to the bar magnet, what is the direction of the magnetic force that the solenoid exerts on the bar magnet?