Download Physics 30 review * Magnetism

5/1/2017
P30 Unit B – Forces and Fields
Part B: Magnetism UA
Name: ____________
Date: ____________
Show all your work on a separate sheet of loose-leaf paper, including starting formulas,
substitutions and diagrams.
1) Compare the motion of a charged particle (q = +11e) as it travels through an individual
gravitational, electric and magnetic field:
a) With a velocity parallel to and in the same direction as the field. (1.5 marks)
b) With a velocity perpendicular to the field. (1.5 marks)
2) An electron is at rest. Can this particle be set into motion by a magnetic field? Explain your
answer. (2 marks)
3) A wire 50 cm long carrying a current of 8.0 A is at right angles to a uniform magnetic field.
The force on the wire is 0.40 N. What is the strength of the magnetic field? (0.10 T) (1
mark)
4) A power line carries a 225 A current from east to west parallel to the surface of the Earth.
a) What is the magnitude of the force acting on each meter of the wire due to Earth’s magnetic
field? (Be = 5.0 x 10-5 T) (0.011 N/m) (1 mark)
b) What is the direction of the force? Explain your answer. (out of the page, or vertically
upwards) (1 mark)
5) A beta particle (high-speed electron) is traveling at right angles to a 0.60 T magnetic field. It
has a speed of 2.5 x 107 m/s.
a) What is the magnitude of the force acting on the particle? (2.4 x 10-12 N) (1 mark)
b) What is the acceleration of this beta particle? (2.6 x 1018 m/s2) (1 mark)
6) An electron is accelerated through a potential difference of 20 000 V, which exists between
P1 and P2. The electron then passes through a small opening in P2 into a uniform magnetic
field of 2.000 T directed into the page.
a) What is the direction of the electric field between the plates P1 and P2? Explain. (to the left)
(1 mark)
P1
P2
v
b) What is the speed of the particle at P2, before entering the B-field? (8.382 x 107 m/s) (2
marks)
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c) Describe the motion of the electron through the magnetic field and the radius the electron
will turn in. (moves clockwise, r = 0.2386 mm) (2 marks)
7) A force of 5.78 x 10-16 N acts on a particle that travels at right angles to a magnetic field. If
the particle moves with a speed of 5.65x 104 m/s and the field has a magnitude of 0.032 T,
how many units of elementary charge does the particle carry? (2.0) (2 marks)
8) Determine the direction of the induced current in each of the following diagrams: (1 mark
each)
9) Suppose that the ion source in a mass spectrometer produces doubly ionized gold ions
(Au2+), each with a mass of 3.27 10-25 kg. The ions are accelerated through a potential
difference of 1.00 kV. Then, a 0.500 T magnetic field causes the particle to follow a circular
path. What is the radius of the path of the particle? (0.0904 m) (3 marks)
10) A square coil of wire is placed in a uniform 0.25 T magnetic field, as shown. Each side has a
length of 0.32 m, and the current in the coil is 12 A (directed clockwise). Determine the
magnitude and direction of the force on each of the four sides of the loop. (0.96 N top (force
directed into the page) and bottom (force directed out of the page) , 0 N left and right)
(2 marks)
B
11) A bar magnet is moved toward a coil of wire that is connected to a sensitive galvanometer, as
shown below:
a) Write to explain what happens to the galvanometer readings in terms of Lenz’s Law as
the north pole of the bar magnet approaches the coils of the wire. (north pole induced on
the right, current from right to left in the galvo) (1 mark)
b) Write to explain what happens to the galvanometer readings in terms of Lenz’s Law as
the north pole of the bar magnet is pulled out of the coils of the wire. (south pole
induced on the right, current from left to right in the galvo) (1 mark)
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