Magnetic Field Strength and Magnetic Force O An electrically charged particle moving in a magnetic field may experience a magnetic force. O Magnetic Field Strength B = F/qv (definition of B, only for v perpendicular to B) B = field strength (N/A.m) or Tesla F = force (N) v = m/s q = charge (C)

O 1 T = 1 N/A.m O The magnetic field is sometimes given in webers per square meter (Wb/m 2 ) when magnetic flux is relevant. O Magnetic field strength = in Gauss (G) = T 1 gauss = T. Tesla = A charge of one coulomb moving with a velocity of one meter per second perpendicular to a magnetic field of one tesla experiences a force of one newton.

O Magnetic Force F = qvB (force on a charged particle, only for v perpendicular to B) F = force (N) q = charge (C) v = velocity (m/s) B = field strength (T) F = qvB sin θ (if the direction of the charge is not perpendicular to the magnetic field)

Problems: O 1. A particle with a charge of -5.0 x C moves at a speed of 1.0 x 10 3 m/s in the +x direction toward a uniform magnetic field of 0.20 T in the +y direction. a.) What is the force on the particle just as it enters the magnetic field? b.) Describe the path of the particle while it is in the field.

O A positive charge of 0.25 C moves horizontally to the right at a speed of 2.0 x 10 2 m/s and enters a magnetic field directed vertically downward. If it experiences a force of 20 N, what is the magnetic field strength? O The magnetic field of the earth is measured at a point on the surface to have a magnitude of 0.6 G and is directed downward and northward, making an angle of about 70 0 with the horizontal. (The earth’s magnetic field varies from place to place. These data are approximately correct for Central U.S.) A proton of charge q = 1.6 x C is moving horizontally in the northward direction with speed 10 7 m/s. Calculate the magnetic force on the proton.

O A charge of C moves vertically in a field of T that is oriented horizontally. What speed must the charge have to experience a force of 10 N?