28. Magnetic Fields and Forces

Which of the following best explains why paperclips are attracted to magnets?

Which of the following materials or objects have scientists successfully levitated using very strong magnetic fields due to their diamagnetic properties?

A rectangular loop of wire is placed near a stationary bar magnet. If the magnet is held stationary and a current is suddenly established in the loop, in which direction does the loop swing relative to the magnet?

Which of the following best describes the direction of the magnetic force on a straight current-carrying wire placed perpendicular to a uniform magnetic field ($B$)?

A stiff wire 50.0 cm long is bent at a right angle in the middle. One section lies along the z axis and the other is along the line y = 2x in the xy plane. A current of 20.0 A flows in the wire—down the z axis and out the wire in the xy plane. The wire passes through a uniform magnetic field given by = (0.285î ) T. Determine the magnitude and direction of the total force on the wire.

A straight, 2.5 m wire carries a typical household current of 1.5 A (in one direction) at a location where the earth's magnetic field is 0.55 gauss from south to north. Find the magnitude and direction of the force that our planet's magnetic field exerts on this wire if it is oriented so that the current in it is running (a) from west to east, (b) vertically upward, (c) from north to south. (d) Is the magnetic force ever large enough to cause significant effects under normal household conditions?

A 5-m current-carrying wire (red line) is ran through a 4 T magnetic field (blue lines), as shown. The angle shown is 30°. What must the magnitude and direction of the current in the wire be when it feels a 3 N force directed into the page?

When a charge moves near a magnetic field, what type of force does it experience?

(III) A curved wire, connecting two points a and b, lies in a plane perpendicular to a uniform magnetic field $\overrightarrow{B}$ and carries a current I. Show that the resultant magnetic force on the wire, no matter what its shape, is the same as that on a straight wire connecting the two points carrying the same current I. See Fig. 27–44.

Using the left-hand rule for generators, the center finger indicates the direction of the $\mathrm{what}$?

Given a straight wire carrying current $I$ placed in a uniform magnetic field $B$, which rule is used to determine the direction of the magnetic force acting on the wire?

Which of the following actions will increase the strength of the magnetic force exerted on a paper clip by a current-carrying wire?

If a magnet is held stationary next to a current-carrying wire, can a current be induced in the wire by the magnet's presence alone?

A straight wire carrying a current ($I$) is placed perpendicular to a uniform magnetic field ($B$) pointing into the page. What is the direction of the magnetic force ($F$) acting on the wire?