Physics 2 
Conceptual Physics
, 10th ed., by Paul Hewitt (San
Francisco, CA: AddisonWesley, 2009).
Written Assignment 3
1.
If 200 volts are put across a 300loop transformer's primary coil:
a.
What will be the voltage output if the secondary coil had 750
loops?
Voltage x N
s
/N
p
200V * 750/300
= 500 volts
b.
What is the power in the secondary coil if the resistance in this
coil is 50 ohms?
Voltage / Resistance
500 / 50
= 10 amps
c.
What is the current drawn in the primary coil?
N
s
/N
p
750 / 300 = 2.5
10A * 2.5
= 25amps
d.
What is the power in the primary coil?
Voltage x amperes
200V * 25A
= 5,000 watts
2.
A model electric train requires 6 volts to operate. If the primary coil
of its transformer has 240 windings, how many windings should the
secondary have if the primary is connected to a 120volt household
circuit?
Secondary Voltage / Primary Voltage x N
p
6 / 120 * 240
= 12 turns
3.
How does the current in the secondary of a transformer compare to
the current in the primary if the voltage in the secondary is three
times the voltage in the primary?
This is stepping up.
There are three times as many turns producing three times the voltage
of the primary. Therefore the primary has a third of the voltage.
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4.
Define the following terms:
a.
Critical angle 
the angle between a ray of light and a surface at
which the ray be completely reflected by the surface
1
. The angle of
incidence is known as the critical angle; it is the largest angle of
incidence for which refraction can still occur.
b.
Total internal reflection –
Also known as total reflection, the
complete reflection of a light ray at the boundary of the medium in
which it is traveling, when the angle of incidence exceeds the
critical angle.
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 Summer '10
 Sohn
 Physics, Total internal reflection, Geometrical optics

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