Workbook 4.7 Solutions

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4.7 Review
1.

In Alberta the north end of a compass needle points to (approximately) the geographic a.
north
b.
south
c.
east
d.
west

2.

An negatively charged droplet travels at a speed of 2.0 x 103 m/s. The field(s) that acts on this droplet is/are
a.
electrical only
b.
electrical and magnetic only
c.
magnetic and gravitational only
d.
electrical, magnetic, and gravitational

3.

A charged particle experience a magnetic force only when it
a.
moves in the same direction as the magnetic field
b.
crosses magnetic field lines
c.
goes against gravity
d.
moves against an electric field

4.

A proton beam travels at a constant velocity to the right as shown below. Use a drawing to help describe the magnetic field created by the beam. [Appendix A] p+

5.

The electromagnet on the right has its poles as labelled.
a. Draw in the battery (between terminals A and B) so that the magnet’s polarity will be as shown in the diagram. [Appendix A] b. Draw the magnetic field lines produced around the electromagnet. [Appendix A]

© Kennedy/Oswald 2008

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S

N

A

B

A

6.

Three particles (A is a neutron, B is an electron
and C is a proton), enter a magnetic field (B) at
the same speed as shown in the diagram. Identify
the direction the particle will be forced. Explain
your choice. [Appendix A]

C

B

A – none (neutral)
B- none (not crossing any field lines)
C – Forced out of the page
7.

Determine the magnetic field strength acting on a positron travelling at 7.31 x 107 m/s experiences a magnetic force of 5.38 x 10-13 N. [0.0460T]

The magnetic field strength is 0.0460T.
8.

A beam of alpha particles is accelerated across a potential difference of 7.50 KV. They are then passed perpendicularly through a magnetic field and turn a circle with a radius of 15.1 cm. Determine the magnetic field strength. [0.117 T]

The magnetic field strength is 0.117 T.

© Kennedy/Oswald 2008

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B

9.

A 6.0 cm long copper wire has a mass of 5.04 g and is carrying a current of 14.10 A perpendicular to a uniform magnetic field. This apparatus is placed in a strong magnetic field and the wire is suspended motionless in the air.

a. Draw a free-body diagram for the wire. [Appendix A]
b. Calculate the magnetic field strength. [0.058 T]

The magnetic field strength is 0.058 T.
10.

A bar magnet is moved relative to a coil, as depicted in the diagrams below. Determine the direction of the electron flow through the galvanometer for each situation. [Appendix A] a.
b.
motion of coil
N

motion of magnet
N

S

G

G

From left to right.
11.

S

From left to right.

A mass spectrometer is used to determine the mass of triply charged negative ions. The ions were first accelerated through a potential difference of 90.0 V, and then injected into a 70.0 mT magnetic field where they have a radius of curvature of 11.6 cm. Determine the mass of the unknown ions. [1.76 x 10-25 kg]

The mass of the ion is 1.76 x 10-25 kg.
© Kennedy/Oswald 2008

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Use the information below to answer question 12.
One end of an iron bar is coiled with insulated wires and
attached to a 10 V AC power supply. The other end of the
iron bar is coiled with twice the length of wire and is
attached to a voltmeter as shown in the diagram
12.

Using the diagram, explain how electrical power is
induced in the secondary coil even though no
current can transfer from the primary. [Appendix A]

primary coil

secondary coil

V
10 V

The changing electric field produces a changing magnetic field in the primary coil which then produces a changing electric field leading to a changing magnetic field in the secondary coil. This allows electric charge in the wire to be influenced by an induced voltage that will cause a reading to register in the secondary coils voltmeter.

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