Exam 29: Magnetic Fields

A coaxial cable has 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 directed upwards with respect to the cable,the effect of the field on the cable is

What value of B should be used in a velocity selector to separate out 2.0-keV protons if E is fixed at 80 kV/m?

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?

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

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?

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 z component of the magnetic field.

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

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 ( )mT)What is the acceleration of the particle?

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?

Equal charges,one at rest,the other having a velocity of 10⁴ m/s,are released in a uniform magnetic field.Which charge has the largest force exerted on it by the magnetic field?

An electron moves in a region where the magnetic field is uniform and has a magnitude of 80 μT.The electron follows 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?

A segment of wire carries a current of 25 A along the x axis from x = −2.0 m to x = 0 and then along the y axis from y = 0 to y = 3.0 m.In this region of space,the magnetic field is equal to 40 mT in the positive z direction.What is the magnitude of the force on this segment of wire?

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 particle (q = 5.0 nC,m = 3.0 μg)moves in a region where the magnetic field has components B_x = 2.0 mT,B_y = 3.0 mT,and B_z = −4.0 mT.At an instant when the speed of the particle is 5.0 km/s and the direction of its velocity is 120° relative to the magnetic field,what is the magnitude of the acceleration of the particle?

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 = 20°,R = 0.50 m,and I = 12A,what is the magnitude of the torque exerted on the loop?

A charged particle moves in a region of uniform magnetic field along a helical path (radius = 5.0 cm,pitch = 12 cm,period = 5.0 ms).What is the speed of this particle as it moves along this path?

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

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 μT.In N,the force exerted by the Earth's magnetic field on the 25 m-long current is

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?

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