Download Lecture 14

• Please sit together
in pairs:
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Onyema and John W.
Alejandra and Dian
Chris and Michael
Ryan and Honglu
John F. and Matt
Walter and Lin
Max and Anwen
Amanda and Mengyue
Pauline and Melissa
Jennifer and Erich
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Alexandra and Irfan
David and Jason
Abigael and Jiayuan
Jake and Erica
Phys 150 Lecture 7
1
Announcements
• Exam 1 solutions available online.
• Homework 7 is due on Sunday, March 10
at midnight.
Phys 150 Lecture 12
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Chapter 6 – Electricity and Magnetism
• Electricity
Van de Graaff
Phys 150 Lecture 12
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i>clicker question
Chemical reactions produce voltages that
are typically
A.
B.
C.
D.
1 volt
100 volts
10,000 volts
1 million volts
Phys 150 Lecture 12
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i>clicker question
Chemical reactions produce voltages that are
typically
Lemon
A.
B.
C.
D.
1 volt = 1 eV per electron
100 volts
10,000 volts
1 million volts
-
Alkaline battery = 1.5 volts
9 volt battery = 6 alkaline batteries
Car battery (Lead – Acid) = 6 2-volt batteries
Lithium ion battery = 3.6 volts
NiMH battery = 1.2 volts
Phys 150 Lecture 12
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i>clicker question
When you get an electric shock from a
door knob, the voltage is typically
A.
B.
C.
D.
1 volt
100 volts
10,000 volts
1 million volts
Phys 150 Lecture 12
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i>clicker question
When you get an electric shock from a
door knob, the voltage is typically
A.
B.
C.
D.
Wimshurst
1 volt
100 volts
10,000 volts – actually, more like 50,000 volts
1 million volts
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Sparks - 30,000 volts/cm (in air)
A spark is an electric current in air
Phys 150 Lecture 12
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i>clicker question
The voltage from an electrical outlet is
A.
B.
C.
D.
a constant 110 volts
a constant 220 volts
varying (average 110 volts)
varying (average 220 volts)
Phys 150 Lecture 12
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i>clicker question
The voltage from an electrical outlet is
A.
B.
C.
D.
a constant 110 volts
a constant 220 volts
varying (average 110 volts)
varying (average 220 volts) – Europe (50 Hz)
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Light string
Varies 60 times/sec (60 Hz)
Alternating current (AC) vs Direct current (DC)
Phys 150 Lecture 12
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i>clicker question
The current through a 10 W LED bulb is
about
A.
B.
C.
D.
0.1 Amps
1 Amp
10 Amps
100 Amps
Phys 150 Lecture 12
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i>clicker question
The current through a 10 W LED bulb is
about
A.
B.
C.
D.
0.1 Amps
1 Amp
10 Amps
100 Amps
P = IV
10 W = I x 110 Volts  I = 0.1 Amps
Phys 150 Lecture 12
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i>clicker question
We use AC for electric power distribution
because
A.
B.
C.
D.
it makes it easy to change voltage
it is less dangerous
most devices require AC current
it is cheaper
Phys 150 Lecture 12
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i>clicker question
We use AC for electric power distribution
because
A.
B.
C.
D.
it makes it easy to change voltage
it is less dangerous
most devices require AC current
it is cheaper
-
High voltage -> Low current (P=IV)
Low current -> Less power loss to heat (I2R)
Power lines
Fuse
Phys 150 Lecture 12
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i>clicker question
An electric spark of 50,000 volts may not
hurt you if
A.
B.
C.
D.
the current is low
the current lasts a very short time
the power is low
Any of the above
Phys 150 Lecture 12
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i>clicker question
An electric spark of 50,000 volts may not
hurt you if
A.
B.
C.
D.
the current is low
the current lasts a very short time
the power is low
Any of the above
-
P = IV
Energy = P x time
Phys 150 Lecture 12
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