PHYS 102 Module 8 - CH 8 and 9 HW (Homework)

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Module 8 - CH 8 and 9 HW (Homework)
PHYS 102

1) The generator at a power plant produces AC at 20,000 V. A transformer steps this up to 325,000 V for
transmission over power lines. If there are 1,900 turns of wire in the input coil of the transformer, how many
turns must there be in the output coil?
turns
30875



Primary voltage: V1 = 20,000 V
Secondary voltage: V2 = 325,000 V
Primary coil turns: n1 = 1,900
Secondary coil turns: n2 = ?

n2 / n1 = V2 / V1

n,900 = 325,000 V /20,000 V
325,000 V
n2 = 1,900 * ( 20,000 V )

n2 = 1,900 * (16.25)
n2 = 30,875


2) What is the wavelength of the 40,000-Hz radio wave used by "radio-controlled" clocks and wristwatches?
m
7500



Velocity: V = 3 * 108 m/s for all Electro Magnetic Waves
Frequency: f = 40,000 Hz
Wavelength: λ = ?

Velocity = frequency * wavelength
V=f*λ

3 * 108 m/s = (40,000 Hz ) * λ
3∗108 m / s
( 40,000 Hz ) = λ

7,500 m = λ


3) A piece of iron is heated with a torch to a temperature of 928 K. How much more energy does it emit as
blackbody radiation at 928 K than it does at room temperature, 298 K?
E928
E298
=
94.04
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Temperature Iron(Hot): T(Hot) = 928 K




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