Exam 22: Magnetic Forces and Magnetic Fields

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

A 500-eV electron and a 300-eV electron trapped in a uniform magnetic field move in circular paths in a plane perpendicular to the magnetic field.What is the ratio of the radii of their orbits?

Two long parallel wires are separated by 4.0 cm.One of the wires carries a current of 20 A and the other carries a 30-A current.Determine the magnitude of the magnetic force on a 2.0-m length of the wire carrying the greater current.

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?

A 2.0-C charge moves with a velocity of ( $2.0 \tilde { \mathbf { i } } + 3.0 \tilde { \mathbf { j } } + 4.0 \tilde { \mathbf { k } }$ )m/s and experiences a magnetic force of ( $4.0 \hat { \mathbf { i } } - 20 \hat { \mathbf { j } } + 12 \hat { \mathbf { k } }$ )N.The x component of the magnetic field is equal to zero.Determine the y component of the magnetic field.

Three coplanar parallel straight wires carry equal currents I to the right as shown below.Each pair of wires is a distance a apart.The direction of the magnetic force on the middle wire

A charged particle (m = 5.0 g,q = -70 $\mu$ C)moves horizontally at a constant speed of 30 km/s in a region where the free fall gravitational acceleration is 9.8 m/s² 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?

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

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 2 500 m/s will have a radius of

A conducting hollow cylinder (inner radius = a,outer radius = b)carries a current of 40 A that is uniformly distributed over the cross section of the conductor.If a = 3.0 mm and b = 6.0 mm,what is the magnitude of the (line)integral $\oint \mathrm { B } \cdot d \mathbf { s }$ around a circular path (radius = 5.0 mm)centered on the axis of the cylinder and in a plane perpendicular to that axis?

A straight wire of length 70 cm carries a current of 50 A and makes an angle of 60 $\degree$ with a uniform magnetic field.If the force on the wire is 1.0 N what is the magnitude of B?

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 ( $40 \hat { \mathbf { i } }$ )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 particle (mass = 2.0 mg,charge = -6.0 $\degree$ C)moves in the positive direction along the x axis with a velocity of 3.0 km/s.It enters a magnetic field of ( $2.0 \tilde { \mathbf { i } } + 3.0 \tilde { \mathbf { j } } + 4.0 \tilde { \mathbf { k } }$ )mT.What is the acceleration of the particle?

Two wires,each having a weight per unit length of 1.0 *10 ^{- 4} N/m,are strung parallel,one 0.10 m above the other.If the wires carry the same current,though in opposite directions,how great must the current in each wire be for the magnetic field of the lower conductor to balance the weight of the upper conductor?

A long,straight wire (radius = 2.0 mm)carries a current of 2.0 A distributed uniformly over a cross section perpendicular to the axis of the wire.What is the magnitude of the magnetic field at a distance of 1.0 mm from the axis of the wire?

Three long,straight,parallel wires all lie in the yz plane and each carries a current of 20 A in the positive z direction.The two outer wires are each 4.0 cm from the center wire.What is the magnitude of the magnetic force on a 50-cm length of either of the outer wires?

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

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?

Three long wires parallel to the x axis carry currents as shown.If I = 20 A,what is the magnitude of the magnetic field at the origin?

Two single charged ions moving perpendicularly to a uniform magnetic field (B = 0.40 T)with speeds of 5 000 km/s follow circular paths that differ in diameter by 5.0 cm.What is the difference in the mass of these two ions?