Exam 8: Magnetic Forces

A particle (q =-4.0 $\mu$ C, m = 5.0 mg) moves in a uniform magnetic field with a velocity having a magnitude of 2.0 km/s and a direction that is 50 $\degree$ away from that of the magnetic field.The particle is observed to have an acceleration with a magnitude of 5.8 m/s2.What is the magnitude of the magnetic field?

A circular loop (radius = 0.50 m) carries a current of 3.0 A and has unit normal vector of ()/3.What is the x component of the torque on this loop when it is placed in a uniform magnetic field of ()T?

A current of 4.0 A is maintained in a single circular loop having a circumference of 80 cm.An external magnetic field of 2.0 T is directed so that the angle between the field and the plane of the loop is 20 $\degree$ .Determine the magnitude of the torque exerted on the loop by the magnetic forces acting upon it.

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?

What is the kinetic energy of an electron that passes undeviated through perpendicular electric and magnetic fields if E = 4.0 kV/m and B = 8.0 mT?

A deuteron is accelerated from rest through a 10-kV potential difference and then moves perpendicularly to a uniform magnetic field with B = 1.6 T.What is the radius of the resulting circular path? (deuteron: m = 3.3 *10-27 kg, q = 1.6*10-19 C)

The reason the north pole of a bar magnet free to rotate points north is because:

A circular coil (radius = 0.40 m) has 160 turns and is in a uniform magnetic field.When the orientation of the coil is varied through all possible positions, the maximum torque on the coil by magnetic forces is 0.16 N . m when the current in the coil is 4.0 mA.What is the magnitude of the magnetic field?

A 2.0-C charge moves with a velocity of () m/s and experiences a magnetic force of () N.The x component of the magnetic field is equal to zero.Determine the y component of the magnetic field.

A particle (mass = 6.0 mg) moves with a speed of 4.0 km/s in a direction that makes an angle of 37 $\degree$ above the positive x axis in the xy plane.At the instant it enters a magnetic field of (5.0) mT it experiences an acceleration of (8.0) m/s2.What is the charge of the particle?

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 () mT.The loop can turn about the y axis.If $\theta$ = 30 $\degree$ , a = 0.40 m, b = 0.30 m, and I = 8.0 A, what is the magnitude of the torque exerted on the loop?

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 a speed V?

A charged particle (mass = 4.0 $\mu$ g, charge = 5.0 $\mu$ C) 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 60 $\degree$ ?

The point P lies along the perpendicular bisector of the line connecting two long straight wires S and T that are perpendicular to the page.A set of directions A through H is shown next to the diagram.When the two equal currents in the wires are directed up out of the page, the direction of the magnetic field at P is closest to the direction of:

An electron moves in a region where the magnetic field is uniform, has a magnitude of 60 $\mu$ T, and points in the positive x direction.At t = 0 the electron has a velocity that has an x component of 30 km/s, a y component of 40 km/s, and a z component of zero.What is the radius of the resulting helical path?

Bert says that a charged particle in a vacuum can travel in a helix only if a uniform electric field and a uniform magnetic field are both present and both parallel to the axis of the helix.Stuart says that only a magnetic field with a component parallel to the axis of the helix is needed.Which one, if either, is correct, and why?

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 travelling in a circle in a uniform 5.00 T magnetic field at a velocity of 2500 m/s will have a radius of:

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

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:

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 $\mu$ s later at point A.What is the magnitude of the magnetic field?