Physics Chapter 28 Review

A particle (mass 2.0 mg, charge = -6.0 μC) moves in the positive direction along the x axis with a velocity of 3.0 km/s. It enters a magnetic field of (2.0i + 3.0j + 4.0k) mT. What is the acceleration of the particle?

(36j - 27k) m/s^2

An unusual lightning strike has a vertical portion with a current of -400 A downwards. The Earth's magnetic field at that location is parallel to the ground and has a magnitude of 30 mT. In N, the force exerted by the Earth's magnetic field on the 25 m-long current is

0.30 N West

An unusual lightning strike has a vertical portion with a positive current of +400 A upwards. The Earth's magnetic field at that location is parallel to the ground and has a magnitude of 30 mT. In N, the force exerted by the Earth's magnetic field on the 25 m-long current is

0.30 N West

A wire (mass 50 g, length 40 cm) is suspended horizontally by two vertical wires which conduct a current I.= 8.0 A, as shown in the figure. The magnetic field in the region is into the paper and has a magnitude of 60 mT. What is the tension in either wire?

0.34 N

A physicist claims that she has found a new particle with a mass 200,000 times the mass of the proton (1.67 ´ 10-27 kg) and a charge of 3.20 ´ 10-19 C. If she is correct, such a particle traveling in a circle in a uniform 5.00 T magnetic field at a velocity of 2500 m/s will have a radius of

0.522 m

A proton is accelerated from rest through a potential difference of 2.5 kV and then moves perpendicularly through a uniform 0.60-T magnetic field. What is the radius of the resulting path?

12 mm

The boundary shown is that of a uniform magnetic field directed in the positive z direction. An electron enters the magnetic field with a velocity pointing along the x axis and exits 0.63 μs later at point A. What is the magnitude of the magnetic field?

14 μT

The figure shows the orientation of a rectangular loop consisting of 80 closely wrapped turns each carrying a current I. The magnetic field in the region is (40i) mT. The loop can turn about the y axis. If θ = 30º, a = 0.40 m, b = 0.20 m, and I = 8.0 A, what is the magnitude of the torque exerted on the loop?

2.7 Nm

A straight wire is bent into the shape shown. Determine the net magnetic force on the wire when the current I travels in the direction shown in the magnetic field B

2IBL in the +z direction

A straight wire of length L carries a current I in the positive Z direction in a region where the magnetic field is uniform and specified bybX = 3B, By = -2B, and Bz = B, where B is a constant. What is the magnitude of the magnetic force on the wire?

3.6 ILB

An electron moves in a region where the magnetic field is uniform and has a magnitude of 80 μT. The electron flows a helical path which has a pitch of 9.0 mm and a radius of 2.0 mm. What is the speed of this electron as it moves in this region?

35 km/s

A charged particle (mass = 4.0 μg, charge 5.0 μC) moves in a region where the only force on it is magnetic. What is the magnitude of the acceleration of the particle at a point where the speed of the particle is 5.0 km/s, the magnitude of the magnetic field is 8.0 mT, and the angle between the direction of the magnetic field and the velocity of the particle is 60º?

43 km/s^2

A charged particle (m = 5.0 g, q = -70 μC) moves horizontally at a constant speed of 30 km/s in a region where the free fall gravitational acceleration is 9.8 m/s^2 downward, the electric field is 700 N/C upward, and the magnetic field is perpendicular to the velocity of the particle. What is the magnitude of the magnetic field in this region?

47 mT

A uniform magnetic field of 0.50 T is directed along the positive x axis. A proton moving with a speed of 60 km/s enters this field. The helical path followed by the proton shown has a pitch of 5.0 mm. Determine the angle between the magnetic field and the velocity of the proton.

51º

The figure shows the orientation of a flat circular loop consisting of 50 closely wrapped turns each carrying a current I. The magnetic field in the region is directed in the positive z direction and has a magnitude of 50 mT. The loop can turn about the y-axis. If θ = 20º, R = 0.50 m, and I = 12A, what is the magnitude of the torque exerted on the loop?

8.1 Nm

A positively charged particle has a velocity in the negative z direction at point P. The magnetic force on the particle at this point is in the negative y direction. Which one of the following statements about the magnetic field at point P can be determined from this data?

Bx is positive

The diagram below shows the position of a long straight wire perpendicular to the page and a set of directions labeled A through H. When the current in the wire is directed up out of the page, the direction of the magnetic field at point P is

C

A magnetic field is directed out of the page. Two charged particles enter from the top and take the paths shown in the figure. Which statement is correct?

Particle 1 has a positive charge and particle 2 has a negative charge

A charged particle (mass = M, charge = Q>0) moves in a region of space where the magnetic field has a constant magnitude of B and a downward direction. What is the magnetic force on the particle at an instant when it is moving horizontally toward the north with speed V?

QVB toward the west

Three particles of equal charge X, Y, and Z, enter a uniform magnetic field B. X has velocity of magnitude V parallel to the field. Y has velocity of magnitude v perpendicular to the field. Z has equal velocity components v parallel and perpendicular to the field. Rank the radii of their orbits from least to greatest.

Rx > Ry > Rz

Equal charges, one at rest, the other having a velocity f 10^4 m/s, are released in a uniform magnetic field. Which charge has the largest force exerted on it by the magnetic field?

The charge that is moving if its velocity is perpendicular to the magnetic field direction when it is released

The magnetic field in a region of space is parallel to the surface of a long flat table. Imagine that this page is lying flat on the table. When current is present in the coil, which is lying on the table, the coil tends to rotate so that the left side moves up and the right side moves down. The magnetic field is

directed parallel to the page and to the right

You stand near the earth's equator. A positively charged particle that starts moving parallel to the surface of the earth in a straight line directed east is initially deflected upwards. If you know there are no electric fields in the vicinity, a possible reason why the particle does not initially acquire a downward component of velocity is because near the equator the magnetic field lines of the earth are directed

from south to north

One reason why we know that magnetic fields are not the same as electric field is because the force exerted on a charge +q

is parallel to an electric field and perpendicular to a magnetic field

An electron moving in the positive x direction experiences a magnetic force in the positive z direction. If Bx.= 0, what is the direction of the magnetic field?

negative y direction

A coaxial cable as an inner cylindrical conductor surrounded by cylindrical insulation and an outer cylindrical conducting shell. The outer shell carries the same current but in the opposite direction from that in the inner conductor as shown. If the coaxial cable sits in a uniform magnetic field direction upwards with respect to the cable, the effect of the field on the cable is

no net force but a slight shift of the inner conductor to the left and the outer conductor to the right

A current loop is oriented in three different positions relative to a uniform magnetic field. In position 1 the plane of the loop is perpendicular to the field lines. In position 2 and 3 the plane of the loop is parallel to the field as shown. The torque on the loop is maximum in

positions 2 and 3

An explorer walks into a lab in a science building. She has a compass in her hand and finds that the south pole of her compass points toward the room's East wall when she is nearer that wall and toward the west wall when she is nearer that wall. You could explain this if magnetized metal had been installed in the East and West walls with North poles pointing into the room. If no magnetic material was installed in the North or South walls of the room, she would expect that

the north pole of the compass would tend to point toward those walls

A straight wire is bent into the shape shown. Determine the net magnetic force on the wire.

zero