Current In Magnetic Field

1. Left diagram: $F$ points upward and $B$ points to the right. Find the direction of $I$.
2. Middle diagram: $I$ points into the page ($\otimes$) and $F$ points to the right. Find the direction of $B$.
3. Right diagram: $I$ points into the page ($\otimes$) and $B$ points to the right. Find the direction of $F$.

1. Left diagram: A rectangular coil lies with its plane perpendicular to $\vec{B}$ (which points out of the page), with current $I$ circulating as shown. Describe its motion.
2. Middle diagram: A rectangular coil lies with its plane perpendicular to $\vec{B}$ (which points into the page), with current $I$ circulating as shown. Describe its motion.
3. Right diagram: A rectangular coil lies with its plane parallel to $\vec{B}$ (which points upward in the plane of the coil), with current $I$ circulating as shown. Describe its motion.

1. In figure (a), with the N pole on the left and the S pole on the right, describe how the coil rotates.
2. In figure (b), the coil rotates clockwise when viewed from above. Identify which side of the magnet is the N pole and which is the S pole.
3. In figure (c), with the S pole on the left and the N pole on the right, the coil rotates counterclockwise when viewed from above. Determine the direction of the current circulating in the coil.

A straight wire 2 m long makes an angle of $30^{\circ}$ with a uniform magnetic field of magnitude $0.050$ T. The wire carries a current of $2$ A. Find the Ampere force on the wire.

In Figure a wire is bent into two mutually perpendicular straight segments and placed in a uniform magnetic field of magnitude $B = 0.10$ T (directed out of the page). The wire carries a current of $2$ A. The horizontal segment from $a$ has length $3$ cm and the vertical segment ending at $b$ has length $4$ cm. Find the resultant force on this bent wire, and show that this force equals the force on a straight wire (carrying the same current) that directly connects the points $a$ and $b$.

1. Find the current $I$ that reduces the tension in the strings to zero.
2. Evaluate $I$ for $l = 50$ cm, $m = 10$ g, $B = 1.0$ T (use $g = 9.8\ \text{m}/\text{s}^2$).
3. Under what conditions will the wire move upward?

In the experiment of Figure to measure magnetic flux density, a coil of $N = 9$ turns hangs from the right pan of a balance with its lower edge of length $l = 10.0$ cm immersed in the magnetic field. When the coil carries a current $I = 0.10$ A, a mass $m = 8.78$ g must be added to the pan to restore balance. Determine the magnetic flux density $B$. (Take $g = 9.8\ \text{m}/\text{s}^2$.)

A square coil is wound from $N = 200$ turns of fine insulated wire, with each side of length $a = 150$ mm. It is placed in a uniform magnetic field of magnitude $B = 0.040$ T. When the coil carries a current of $I = 8.0$ A, find the maximum torque acting on the coil.

A small circular coil of $N = 20$ turns and radius $r = 4$ cm is placed in a uniform magnetic field of magnitude $B = 0.050$ T. The normal to the coil plane makes a $60^{\circ}$ angle with $\vec{B}$. The coil carries a current $I = 3$ A. Find the torque on the coil.

A rectangular coil is wound from $N = 50$ turns of insulated fine wire; its sides are $10$ cm and $5$ cm long, and it carries a current $I = 0.10$ A. The coil can rotate about one of its sides, $OO'$ (see Figure 14.34). A uniform external magnetic field of magnitude $B = 0.050$ T is applied so that $\vec{B}$ makes a $30^{\circ}$ angle with the plane of the coil. Find the torque on the coil.