physics 2 lecture 5 - electrostatics and electrodynamics
TRANSCRIPT
8/11/2019 Physics 2 Lecture 5 - Electrostatics and Electrodynamics
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LESSON 5
Prepared by :
Pro f. Michael M. Salvahan
Electrostatics and Electrodynamics
8/11/2019 Physics 2 Lecture 5 - Electrostatics and Electrodynamics
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Quo te for the Day
No mat ter how many
m is takes you make or howslow you progress, you
are st i l l way ahead ofeveryone who isn’t try ing .
8/11/2019 Physics 2 Lecture 5 - Electrostatics and Electrodynamics
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Electr ic Charge
Two Kinds of Electric Charge
1. Positive
2. Negative
Electric charge is conserved.
“If a certain amount of one type ofcharge is produced in a process, an equal
amount of opposite type is produced.”
8/11/2019 Physics 2 Lecture 5 - Electrostatics and Electrodynamics
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Electr ic Charge
Electric Charge
1. Proton Charge = 1.602 x 10-19 C
2. Electron Charge = - 1.602 x 10-19
C
1 C = 6.25 x 1018 e
1 e = 1.602 x 10-19 C
8/11/2019 Physics 2 Lecture 5 - Electrostatics and Electrodynamics
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Coulomb’s Law
Coulomb’s Law
Suppose that two point charges, Q1 and
Q2 are at a distance r apart in vacuum, If Q1and Q2 have the same sign, the two charges
repel each other, if they have opposite signs,
they attract each other.
= 2
2 k = 1
4 πε
(in vacuum) k = 9 x109 •2
2
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Coulomb’s Law
Coulomb’s Law
When the surrounding medium is not a
vacuum, forces caused by induced charges inthe material reduce the force between point
charges. If a material has a dielectric
constant K, then εo will be replaced by Kεo =
ε.
= 2
• 2 k =
1
4 πε
K = ε / εo
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Coulomb’s Law
Sample Problems
1. A glass rod rubbed with silk acquires a
charge of +80.0 x 10
-10
C.
a. What is the charge on the silk?
b. How many electrons have been
transferred to the silk?
a. – 80.0 x 10-10 C
b. No. of electrons = 5.00 x 10
10
electrons
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Coulomb’s Law
Sample Problems
2. Two particles having a charge of -1.0 μC
and -2.0 μC are separated by a distance of0.30m. What is the electrostatic force on each
particle?
F = 0.20 N
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Coulomb’s Law
Sample Problems
3. Two charges are separated to distance of
100 cm, causing the electric force betweenthem to increase by a factor of exactly 5.
What was their initial separation distance?
r 1 = 2.24 m
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Coulomb’s Law
Sample Problems
4. Two coins lie 1.5 m apart on a table. They
carry identical charges. Approximately howlarge is the charge on each if a coin
experiences a force of 2 N?
Q = 2 x 10-5 C
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Coulomb’s Law
Sample Problems
5. An isolated electron experiences an electric
force of 3.2 x 10
-14
N. What is the electric fieldat the electric location?
E = 2.0 x 105 N/C
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Coulomb’s Law
Sample Problems
6. A proton is accelerated eastward at 1.84 x
10
9
m / s
2
by an electric field. Determine themagnitude and direction of the electric field.
mp = 1.673 x 10-27 kg
E = 19.25 N/C, eastward