Exam 24: Magnetic Fields and Forces

Two long parallel wires placed side-by-side on a horizontal table carry identical current straight toward you. From your point of view, the magnetic field at a point exactly between the two wires

At a point 10 m away from a long straight thin wire, the magnetic field due to the wire is 0.10 mT. What current flows through the wire? (?₀ = 4? × 10^-7 T ? m/A)

If a calculated quantity has units of $\frac { \mathrm { N } \cdot \mathrm { s } } { \mathrm { C } \cdot \mathrm { m } }$ , that quantity could be

A long straight wire on the z-axis carries a current of 8.0 A in the +z direction (out of the paper). A circular loop of radius 10 cm lies in the xy-plane and carries a 3.0-A current, as shown in the figure. Point P, at the center of the loop, is 25 cm from the z-axis. An electron is projected from P with a velocity of 3.0 × 10⁶ m/s in the -x direction. What is the y component of the magnetic force on the electron? (e = 1.60 × 10^-19, μ₀ = 4π × 10^-7 T ∙ m/A)

A ring with a clockwise current (as viewed from above the ring)is situated with its center directly above another ring, which has a counter-clockwise current, as shown in the figure. In what direction is the net magnetic force exerted on the top ring due to the bottom ring?

An ideal solenoid with 400 turns has a radius of 0.040 m and is 40 cm long. If this solenoid carries a current of 12 A, what is the magnitude of the magnetic field at the center of the solenoid? (μ₀ = 4π × 10^-7 T ∙ m/A)

A flat rectangular loop of wire is placed between the poles of a magnet, as shown in the figure. It has dimensions w = 0.60 m and L = 1.0 m, and carries a current I = 2.0 A in the direction shown. The magnetic field due to the magnet is uniform and of magnitude 0.80 T. The loop rotates in the magnetic field and at one point the plane of the loop makes a 30° angle with the field. At that instant, what is the magnitude of the torque acting on the wire due to the magnetic field?

A charged particle is observed traveling in a circular path of radius R in a uniform magnetic field. If the particle were traveling twice as fast, the radius of the circular path would be

When two long parallel wires carry unequal currents, the magnitude of the magnetic force that one wire exerts on the other is F. If the current in both wires is now doubled, what is the magnitude of the new magnetic force on each wire?

We observe that a moving charged particle experiences no magnetic force. From this we can definitely conclude that

An ideal solenoid 20 cm long is wound with 5000 turns of very thin wire. What strength magnetic field is produced at the center of the solenoid when a current of 10 A flows through it? (μ₀ = 4π × 10^-7 T ∙ m/A)

An ideal solenoid of length 10 cm consists of a wire wrapped tightly around a wooden core. The magnetic field strength is $4.0 \mathrm {~T}$ inside the solenoid. If the solenoid is stretched to $25 \mathrm {~cm}$ by applying a force to it, what does the magnetic field become?

For the horseshoe magnet shown in the figure, the left end is a north magnetic pole and the right end is a south magnetic pole. When the switch is closed in the circuit, which way will the wire between the poles of the horseshoe magnet initially deflect?

A current-carrying loop of wire lies flat on a horizontal tabletop. When viewed from above, the current moves around the loop in a counterclockwise sense. For points on the tabletop inside the loop, the magnetic field lines caused by this current

A thin copper rod 1.0 m long has a mass of 0.050 kg and is in a magnetic field of 0.10 T. What minimum current in the rod is needed in order for the magnetic force to balance the weight of the rod?