Exam 24: Magnetic Fields and Forces

An electron moving perpendicular to a uniform magnetic field of 0.22 T moves in a circle with a speed of 1.5 × 10⁷ m/s. What is the radius of the circle? (e = 1.60 × 10^-19 C, m_electron = 9.11 × 10^-31kg)

Two long parallel wires separated by 7.5 cm each carry 3.3 A in opposite directions. (μ₀ = 4π × 10^-7 T ∙ m/A) (a) What magnetic force per length acts on each of the wires? Is it attractive or repulsive? (b) Find the magnitude of the magnetic field midway between the two wires.

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

A positive charge is moving to the right and experiences an upward magnetic force, as shown in the figure. In which direction must the magnetic field have a component?

Two long parallel wires that are 0.40 m apart carry currents of 10 A in opposite directions. What is the magnetic field strength in the plane of the wires at a point that is 20 cm from one wire and 60 cm from the other? (μ₀ = 4π × 10^-7 T ∙ m/A)

A long, straight wire carrying a current is placed along the y-axis. If the direction of the current is in the +y direction, what is the direction of the magnetic field due to this wire as you view it in such a way that the current is coming directly toward you?

A proton moving eastward with a velocity of 5.0 km/s enters a magnetic field of 0.20 T pointing northward. What are the magnitude and direction of the force that the magnetic field exerts on the proton? (e = 1.60 × 10^-19C)

A flat circular coil has 250 identical loops of very thin wire. Each loop has an area of 0.12 m² and carries 15 mA of current. This coil is placed in a magnetic field of 0.050 T oriented at 30° to the plane of the loop. What is the magnitude of the magnetic moment of the coil?

A high power line carries a current of 1.0 kA. What is the strength of the magnetic field this line produces at the ground, 10 m away? (μ₀ = 4π × 10^-7 T ∙ m/A)

A proton having a speed of 3.0 × 10⁶ m/s in a direction perpendicular to a uniform magnetic field moves in a circle of radius 0.20 m within the field. What is the magnitude of the magnetic field? (e = 1.60 × 10^-19 C, m_proton = 1.67 × 10^-27 kg)

Two long parallel wires that are 0.30 m apart carry currents of 5.0 A and 8.0 A in the opposite direction. Find the magnitude of the force per unit length that each wire exerts on the other wire and indicate if the force is attractive or repulsive. (μ₀ = 4π × 10^-7 T ∙ m/A)

Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires are separated by 20 cm. At what point between the two wires do they produce the same strength magnetic field?

An electron moves with a speed of 8.0 × 10⁶ m/s along the +x-axis. It enters a region where there is a magnetic field of 2.5 T, directed at an angle of 60° to the +x-axis and lying in the xy-plane. Calculate the magnitude of the acceleration of the electron. (e = 1.60 × 10^-19 C, m_e1 = 9.11 × 10^-31 kg)

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 cm by applying a force to it, what does the magnetic field become?

Which one of the following statements is correct?

A proton, moving north, enters a magnetic field. Because of this field, the proton curves downward. We may conclude that the magnetic field must have a component

The maximum torque on a flat current-carrying loop occurs when the angle between the plane of the loop's area and the magnetic field vector is

A flat circular coil has 200 identical loops of very thin wire. Each loop has an area of 0.12 m² and carries 0.50 A of current. This coil is placed in a magnetic field of 0.050 T oriented at 30° to the plane of the loop. What is the magnitude of the magnetic torque on the coil?

A long straight wire carrying a 4-A current is placed along the x-axis as shown in the figure. What is the direction of the magnetic field at a point P due to this wire?

A flat circular wire loop lies in a horizontal plane on a table and carries current in a counterclockwise direction when viewed from above. At this point, the earth's magnetic field points to the north and dips below the horizontal. Which side of the coil tends to lift off of the table due to the magnetic torque on the loop?