Physics 1100 In-Class Problems: Magnetism

1. In the diagrams below, draw or indicate the direction of the magnetic force on the moving charge and calculate its magnitude.The magnetic field may be into or out of the page the page or at an angle to the positive x axis.
   

   (a) q = +5.0 μC, v = 15.0 × 103 m/s, B = 0.25 T, θ = 65°	(b) q = -3.0 μC, v = 6.0 × 103 m/s, B = 0.25 T, θ = 122°
   (c) q = +5.0 μC, v = 15.0 × 103 m/s, B = 0.25 T	(d) q = -5.0 μC, v = 15.0 × 103 m/s, B = 0.25 T
   (e) q = +5.0 μC, v = 15.0 × 103 m/s, B = 0.25 T	(f) q = -5.0 μC, v = 15.0 x× 103 m/s, B = 0.25 T

2. A beam of protons moves in a circle of radius 0.25 m. The beam moves perpendicular to a 0.30 T magnetic field. (a) What is the speed of each proton? (b) Determine the magnitude of the centripetal force on each proton. The mass of a proton is m_P = 1.67 × 10^-27 kg and it has a charge of +e where e = 1.609 × 10^-19 C.
   

3. A mass spectrometer uses a potential difference of 2.00 kV to accelerate a singly charged ion (+e) to high speed. It enters a mass spectrometer where a 0.400-T magnetic field then bends the ion into a circular path of radius 0.226 m. What is the mass of the ion? Multiply this mass by Avagadro's Number, 6.022 × 10²³, and you get the atomic mass of a mole of these atoms in kg. Use a periodic table to identify the element.

4. Suppose that an ion source in a mass spectrometer produces doubly ionized gold ions (Au⁺⁺), each with a mass of 3.27 × 10^-25 kg. The ions are accelerated from rest through a potential difference of 1.00 kV. Then, a 0.500-T magnetic field causes the ions to follow a circular path. Determine the radius of the path.
   

5. A electric power line carries a current of 1400 A in a location where the earth's magnetic field is 5.0 × 10^-5 T. The line makes an angle of 75° with respect to the field. Determine the magnitude of the magnetic force on a 120-m length of line.
   

6. In the diagram below, a 6.00 m long wire carrying a conventional current of 120 A is immersed in a uniform magnetic field of magnitude 0.200 T and width 3.50 m. Determine the magnetic force on the wire.
   

   
   

7. A charge of +55 μC and mass 0.013 kg has, at the moment shown below, a speed of 15000 m/s in the direction shown. It is travelling in a region near the surface of the earth where the magnetic field is uniform and has a magnitude of 0.125 T. There is also an electric field E = 2500 N/C. Draw a free body diagram showing all three forces and determine the acceleration of the charge. The velocity of the charge is perpendicular to the magnetic field but makes an angle of 40.0° with the electric field.
   

   

8. In diagram A below, two wires are carrying conventional currents, I₁ = 30.0 A and I₂ = 22.0 A, in opposite directions. Diagram B gives a head on perspective. Determine the direction and magnitude of the net magnetic field at points A, B, and C where r₁ = 0.250 m, r₂ = 0.350 m, r₃ = 0.700 m, and r₄ = 0.500 m.
   

   
   

9. Determine the direction and magnitude of the net magnetic field at point A and B due to the two wires shown below. The wires carry conventiona currents I₁ = 650 mA and I₂ = 475 mA. Point A is a distance r₁ = 1.20 m from wire 1 and point B is r₂ = 2.20 m away.
   

   
   

Questions? mike.coombes@kwantlen.ca