HW 4.1 Physics Magnetism

The force on a charged particle created by its motion in a magnetic field is maximum at what angle between the particle velocity and field? a. zero b. 90° c. 180° d. 45°

Correct b. 90°

Two singly ionized isotopes, X and Y, of the same element move with the same speed perpendicular to a uniform magnetic field. Isotope X follows a path of radius 3.37 cm while isotope Y moves along a path 3.58 cm in radius. What is the ratio of the two isotope masses, (mX/my) ? a. 0.941 b. 1.06 c. 0.886 d. 1.13 e. Not enough information is given.

a. 0.941

A stationary positive charge + Q is located in a magnetic field B, which is directed toward the right as indicated. The direction of the magnetic force on Q is: a. There is no magnetic force. b. down. c. up. d. toward the right

a. There is no magnetic force.

If an electron is released at the equator and falls toward the Earth under the influence of gravity, the magnetic force on the electron will be toward the: a. west. b. south. c. north. d. east.

a. west.

An electron moves through a region of crossed electric and magnetic fields. The electric field E = 2 300 V/m and is directed straight down. The magnetic field B = 0.95 T and is directed to the left. For what velocity v of the electron into the paper will the electric force exactly cancel the magnetic force? a. 2 200 m/s b. 2 400 m/s c. 4 400 m/s d. 3 800 m/s e. 3 500 m/s

b. 2 400 m/s

A proton is released such that it has an initial speed of 4.1 × 10 5 m/s from left to right across the page. A magnetic field of 0.8 T is present at an angle of 45° to the horizontal direction (or positive x axis). What is the magnitude of the force experienced by the proton? ( qp = 1.6 × 10 −19 C) b. 3.7E-14 N c. 5.9E-33 N d. 9.3E-33 N e. 4.5E-14 N

b. 3.7E-14 N

A proton moves through a magnetic field of magnitude 1.40 T with speed 5.00 &αχυτε;&νβσπ; 106 m/s. What is the magnitude of the maximum acceleration of the proton? The mass of a proton is 1.67 &αχυτε;&νβσπ;10 -27 kg, and its charge is 1.6 &αχυτε;&νβσπ;10 -19 C. a. 3.35E+21 m/s2 b. 6.71E+14 m/s2 c. 1.71E+21 m/s2 d. 3.42E+14 m/s2

b. 6.71E+14 m/s2

A proton is released such that its initial velocity is from right to left across this page. The proton's path, however, is deflected in a direction toward the bottom edge of the page due to the presence of a uniform magnetic field. What is the direction of this field? a. from bottom edge to top edge of the page b. into the page c. from right to left across the page d. out of the page

b. into the page

In a mass spectrometer, an ion will have a smaller radius for its circular path if: a. its speed is greater. b. its charge is greater. c. the magnetic field is weaker. d. its mass is greater.

b. its charge is greater.

There is a magnetic force on a particle. It is possible that the particle is: a. moving in the direction of the magnetic field. b. not part of a wire. c. stationary. d. uncharged.

b. not part of a wire.

At the Fermilab accelerator in Weston, Illinois, singly-charged ions with momentum 3.3 × 10 −16 kg ⋅m/s are held in a circular orbit of radius 1.00 km by an upward magnetic field. What B field must be used to maintain the ions in this orbit? ( q ion = 1.60 × 10 −19 C) a. 0.48 T b. 0.19 T c. 2.1 T d. 5.3 T

c. 2.1 T

When a magnetic field causes a charged particle to move in a circular path, the only quantity listed below which the magnetic force changes significantly as the particle goes around in a circle is the particle's: a. radius for the circle. b. energy. c. momentum. d. time to go around the circle once.

c. momentum.

A proton and a deuteron are moving with equal velocities perpendicular to a uniform magnetic field. A deuteron has the same charge as the proton but has twice its mass. The ratio of the magnetic force on the proton to that on the deuteron is: a. 2. b. There is no magnetic force in this case. c. 0.5. d. 1.

d. 1.

Different units can be used to measure the same physical quantity, differing only by some multiplicative factor. The cgs unit for magnetic field, the gauss, is equal to ________ tesla. a. 104 b. These units do not measure the same physical quantity. c. 0.5 d. 10-4

d. 10-4

A proton and a deuteron are moving with equal velocities perpendicular to a uniform magnetic field. A deuteron has the same charge as the proton but has twice its mass. The ratio of the acceleration of the proton to that of the deuteron is: a. 1. b. There is no acceleration in this case. c. 0.5. d. 2.

d. 2.

If a charged particle is moving in a uniform magnetic field, its path can be: a. a straight line. b. a circle. c. a helix. d. any of the above.

d. any of the above.

If a proton is released at the equator and falls toward the Earth under the influence of gravity, the magnetic force on the proton will be toward the: a. west. b. north. c. south. d. east.

d. east.

A proton moves across the Earth's equator in a northeasterly direction. At this point the Earth's magnetic field has a direction due north and is parallel to the surface. What is the direction of the force acting on the proton at this instant? a. toward the northwest b. toward the northeast c. into the Earth's surface d. out of the Earth's surface

d. out of the Earth's surface

The path of a charged particle moving parallel to a uniform magnetic field will be a a. circle. b. ellipse. c. parabola. d. straight line.

d. straight line.

Assume that a uniform magnetic field is directed into this page. If an electron is released with an initial velocity directed from the bottom edge to the top edge of the page, which of the following describes the direction of the resultant force acting on the electron? a. to the left b. into the page c. out of the page d. to the right

d. to the right