Which one of the following statements is true? A. Like positive and negative charges, science has been able to separate north and south magnetic poles. B. Science has been able to separate a north magnetic pole from a south magnetic pole, but not a south magnetic pole from a north magnetic pole. C. Unlike positive and negative charges, science has never been able to separate north and south magnetic poles. D. Science has been able to separate a south magnetic pole from a north magnetic pole, but not a north magnetic pole from a south magnetic pole.

A particle’s path is bent when it passes through a region of non-zero magnetic field although its speed remains unchanged. This is very useful for “beam steering’’ in particle accelerators. Consider a proton of speed 4106m/s entering a region of uniform magnetic field 0.2 T over a 5-cm-wide region. Magnetic field is perpendicular to the velocity of the particle. By how much angle will the path of the proton be bent? (Hint: the particle comes out tangent to a circle.

A wire carrying a 30.0-A current passes between the poles of a strong magnet that is perpendicular to its field and experiences a 2.16-N force on the 4.00 cm of wire in the field. What is the average field strength?

The right-hand rule is a way to determine the direction of the magnetic field produced by moving charges. Imagine wrapping your right hand around the path of the charges so that the positive charges (or the current) flow from the little finger side of your fist to the thumb side (Figure 8.53). Then your fingers circle the path in the same direction as the magnetic field lines. Use this rule to verify the directions of the magnetic fields shown in Figures 8.8 and 8.10. How would you use the rule to find the direction of the magnetic field lines around a moving negative charge?

(a) A dc power line for a light-rail system caries 1000 A at an angle of 30.0 to Earth's 5.0105 T field, What is the force on a 100-m section of this line? (b) Discuss practical concerns this presents, if any.

A proton track passes through a magnetic field with radius of 50 cm. The magnetic field strength is 1.5 T. What is the total energy of the proton?

A laboratory electromagnet produces a magnetic field of magnitude 1.50 T. A proton moves through this field with a speed of 6.00 106 m/s. (a) Find the magnitude of the maximum magnetic force that could he exerted on the proton. (b) What is the magnitude of the maximum acceleration of the proton? (c) Would the field exert the same magnetic force on an electron moving through the field with the same speed? (d) Would the electron experience the same acceleration? Explain.

Unreasonable Results (a) Find the charge on a baseball, thrown at 35.0 m/s perpendicular to the Earth’s 5.00105T field, that experiences a 1.00-N magnetic force. (b) What is unreasonable about this result? (c) Which assumption or premise is responsible?

(a) A physicist performing a sensitive measurement wants to limit the magnetic force on a moving charge in her equipment to less than 1.001012N. What is the greatest the charge can be if it moves at a maximum speed of 30.0 m/s in the Earth’s field? (b) Discuss whether it would be difficult to limit the charge to less than the value found in (a) by competing it with typical static electricity and noting that static is often absent.

Unreasonable Results A charged particle having mass 6.641027kg (that of a helium atom) moving at 8.70105m/s perpendicular to a 1.50T magnetic field travels in a circular path of radius 16.0 mm. (a) What is the charge of the particle? (b) What is unreasonable about this result? (c) Which assumptions are responsible?