Magnitudes of a Magnetic Field
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1. A proton traveling at 3.5 x 106 m/s passes perpendicular to a uniform magnetic field of 4.2 x 10-2 T.
What is the magnitude of the force on the proton while the proton is in the magnetic field?
2. A uniform 1.5 T magnetic field points north. If an electron moves vertically downward (toward the
ground) with a speed of 2.5 x 107 m/s through this field, what force (magnitude and direction) will act
on it?
3. A proton moves straight upward (away from the ground) through a uniform field that points from east to
west and has a magnitude of 2.5 T. If the proton moves with a speed of 1.5 x 107 m/s through this field,
what force (magnitude and direction) will act on it?
4. A proton traveling to the right along the x-axis enters a region where there is a magnetic field of
magnitude 2.5 T directed upward along the y-axis. If the proton experiences a force of 3.2 x 10-12 N,
find the speed of the proton.
5. If an electron in an electron beam experiences a force of 2.0 x 10-14 N down while traveling north at a
speed of 1.5 x 106 m/s, then what is the magnitude and direction of the magnetic field that deflects the
electron?
6. An alpha particle (the nucleus of a helium atom, carrying a charge of 3.2 x 10-19 C) moves at 5.5 x 107
m/s at a right angle to a magnetic field. If the particle experiences a force of 1.5 x 10-14 N due to the
magnetic field, then what is the magnitude of the magnetic field?
Force on a Current-Carrying Conductor
1. A wire 1.0 m long experiences a magnetic force of 0.50 N due to a perpendicular uniform magnetic
field. If the wire carries a current of 10.0 A, what is the magnitude of the magnetic field?
2. The magnetic force acting on a wire that is perpendicular to a 1.5 T uniform magnetic field is 4.4 N. If
the current in the wire is 5.0 A, what is the length of the wire that is inside the magnetic field?
3. A 2.5 N magnetic force acts on a 475 m wire that is perpendicular to a 0.50 T magnetic field. What is
the current in the wire?
4. The magnetic force on a straight 0.15 m segment of wire carrying a current of 4.5 A is 1.0 N. What is
the magnitude of the component of the magnetic field that is perpendicular to the wire?
Induced EMF and Current
1. A single circular loop with a radius of 22 cm is placed in a uniform external magnetic field with a
strength of 0.50 T so that the plane of the coil is perpendicular to the field. The coil is pulled steadily
out of the field in 0.25 s. Find the average induced emf during this interval.
2. A coil with 205 turns of wire, a total resistance of 23 , and a cross-sectional area of 0.25 cm2 is
positioned with its plane perpendicular to the field of a powerful electromagnet. What average current is
induced in the coil during the 0.25 s that the magnetic field drops from 1.6 to 0.0 T?
3. A circular wire loop with a radius of 0.33 m is located in an external magnetic field of strength +0.35 T
that is perpendicular to the plane of the loop. The field strength changes to -0.25 T in 1.5 s. (The plus
and minus signs for a magnetic field refer to opposite directions through the coil.) Find the magnitude
of the average induced emf during this interval.
4. A 505-turn circular loop with a diameter of 15.5 cm is initially aligned so that the plane is perpendicular
to the Earth’s magnetic field. In 2.77 ms the coil is rotated 90.0 so that its plane is parallel to the
Earth’s magnetic field. If the average emf of 0.166 V is induced in the coil, what is the value of the
Earth’s magnetic field?