Exam 28: Magnetic Fields

In a certain mass spectrograph, an ion beam passes through a velocity filter consisting of mutually perpendicular fields and .The beam then enters a region of another magnetic field perpendicular to the beam.The radius of curvature of the resulting ion beam is proportional to:

A current is clockwise around the outside edge of this page and a uniform magnetic field is directed parallel to the page, from left to right.If the magnetic force is the only force acting on the page, the page will rotate so the right edge:

An electron is launched with velocity in a uniform magnetic field .The angle $\theta$ between and is between 0 and 90^o.As a result, the electron follows a helix, its velocity vector returning to its initial value in a time interval of:

The resonance condition in a cyclotron states that:

The diagrams show five possible orientations of a magnetic dipole in a uniform magnetic field .For which of these is the potential energy the greatest?

An electron and a proton both each travel with equal speeds around circular orbits in the same uniform magnetic field, as shown in the diagram (not to scale).The field is into the page on the diagram.Because the electron is less massive than the proton and because the electron is negatively charged and the proton is positively charged:

The units of magnetic dipole moment are:

Units of a magnetic field might be:

Which is NOT one of the differences between a cyclotron and a synchrotron?

An electron moves in the negative x direction, through a uniform magnetic field that is in the negative y direction.The magnetic force on the electron is:

At one instant an electron is moving in the positive x direction along the x axis in a region where there is a uniform magnetic field in the positive z direction.When viewed from a point on the positive z axis, it subsequent motion is:

The magnetic dipole moment of a current-carrying loop of wire is in the positive z direction.If a uniform magnetic field is in the positive x direction the magnetic torque on the loop is:

A conducting strip of width 1.5 mm is in a magnetic field.As a result, there is a potential difference of 4.3 mV across the width of the strip.What is the magnitude of the electric field in the strip?

An ion with a charge of +3.2 * 10⁻¹⁹ C is in region where a uniform electric field of 5 *10^4.V/m is perpendicular to a uniform magnetic field of 0.8 T.If its acceleration is zero then its speed must be:

An electron is launched with velocity in a uniform magnetic field .The angle $\theta$ between and is between 0 and 90^o.As a result, the electron follows a helical path.The pitch of the helix is:

A static magnetic field CANNOT:

A charged particle is projected into a region of uniform, parallel, and fields.The force on the particle is:

The magnetic torque exerted on a flat current-carrying loop of wire by a uniform magnetic field is:

An electron enters a region of uniform perpendicular and fields.It is observed that the velocity of the electron is unaffected.A possible explanation is:

An electron is travelling in the positive x direction.A uniform electric field is in the negative y direction.If a uniform magnetic field with the appropriate magnitude and direction also exists in the region, the total force on the electron will be zero.The appropriate direction for the magnetic field is: