chapter 20 static electricity
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Chapter 20 Static Electricity. Electrostatics - The study of electrical charges that can be collected and held in one place. Chapter 20 Static Electricity. Chapter 20 Static Electricity. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 20 Static Electricity Electrostatics - The study of electrical
charges that can be collected and held in one place.
Chapter 20Static Electricity
Charge Size
Proton Positive 1.67 x 10-27kg
Electron Negative 9.11 x 10-31 kg
Neutron Neutral 1.67 x 10-27 kg
Chapter 20Static Electricity Every atom is composed of a positively charged
nucleus, around which are distributed a number of negatively charged electrons.
Electrons of all atoms are the same. Each has the same quantity of negative charge and the same mass.
Protons and neutrons compose the nucleus. Protons are 2000 times more massive than an electron and carry an equal amount of charge.
All normal atoms have equal number of protons and electrons.
Chapter 20Static Electricity
Chapter 20Static Electricity
Chapter 20Static Electricity
Charged versus Uncharged Objects
•Positively-Charged Possesses more protons than electrons
•Negatively-Charged Possesses more electrons than protons
•Uncharged Equal numbers of protons and electrons
Chapter 20Static Electricity
Electric Charge:• Positive or negative• Charge is quantified• Like charges repel, opposites attract• Charges exert a force through a distance.• The force is stronger when the charges are close together
Chapter 20Static Electricity
Chapter 20Static Electricity
Chapter 20Static Electricity
Chapter 20Static Electricity Grounding Connecting a charged object to
earth to remove an object’s charge. Conductor Any material through which an
electric charge is readily transferred. Insulator Any material through which an
electric charge is not readily transferred. Induction The process of charging an object
by bringing it into the electric field of another object.
Chapter 20Static Electricity
Chapter 20Static Electricity
Chapter 20Static Electricity
- +
Charge by Conduction
Chapter 20Static Electricity
+
+ + +
-
++
+
++
+
Charge by Induction
Chapter 20Static Electricity
Chapter 20Static Electricity
Chapter 20Static Electricity
Chapter 20Static Electricity
Coulomb The quantity of electric charge
1 coulomb = 6.25 x 1018 electrons
1 electron = 1.6 x 10-19 coulombs
Chapter 20Static Electricity
Coulomb’s Law The force between two charged objects vary directly with the product of their charges and inversely as the square of the distances between them.
221
d
qqkF
F force (N)q charge (C)k 9 x 109 N •m2/ C2
Inverse Square Law
Chapter 20Static Electricity
F kq1q2
d2
q1 = 1 x 10-4 Cq2 = -5 x 10-5 CD = .5 mk = 9 x 109 N •m2/ C2
Find the force of attraction between charges of 100 µC and -50 µC separated by a distance of 50 cm.
F (9x109 N m2 / C2 )(1x10 4 C)(-5x10 5 C)
(.5 m)2
Chapter 20Static Electricity
Find the force of attraction between charges of 100 µC and -50 µC separated by a distance of 50 cm.
F (9x109 N m2 / C2 )(1x10 4 C)(-5x10 5 C)
(.5 m)2
F = -180 N The negative means a force of attraction
Chapter 20Static Electricity
F kq1q2
d2
q1 = 5 x 10-6 Cq2 = 3 x 10-6 CD = .04 mk = 9 x 109 N •m2/ C2
Two charges are separated by 4.0 cm. Object A has a charge of +5 µC and object B has a charge of +3 µC. What is the force on object A?
F (9x109 N m2 / C2 )(5x10 6 C)(3x10 6 C)
(.04 m)2
Chapter 20 Static Electricity
Two charges are separated by 4.0 cm. Object A has a charge of +5 µC and object B has a charge of +3 µC. What is the force on object A?
F = 84 N The positive means a force of repulsion
F (9x109 N m2 / C2 )(5x10 6 C)(3x10 6 C)
(.04 m)2
Chapter 20Static Electricity
A positive charge of 3.5 x 10-6 C has 2 charges nearby. One has a negative charge of -1.2 x 10-6 C and is .03 m away at 180°. The second charge is a positive charge of 3 x 10-6 C at 270° at .02 m.
What is the total force on the 3.5 x 10-6 C charge?
Chapter 20Static Electricity
+
+
-
.03 m
.02 m
+
F2
F1
Chapter 20Static Electricity
+
F2
F1
F1
(9x109N m2 / C2 )(3.5 x106 C)(1.2x10 6C)(.03m)2
F1 = 42 N
F2
(9x109N m2 / C2 )(3.5 x106 C)(3x106 C)(.02m)2
F2 = 236 N
Chapter 20Static Electricity
F1 = 42 N
+
F2 = 236 NF2 = (42 N)2+ (236 N)2 = 57460 F
F = 240 N
tan = 42 N/236 N = .178
= 10°
The force on the 3.5 x 10-6C is 240 N at 100º
Chapter 20Static Electricity
A negative charge of 4.5 µ C has 2 charges nearby. One has a negative charge of 1.2 µ C and is .04 m away at 90°. The second charge is a negative charge of 2.1µ C at 180° at .03 m.
What is the total force on the 4.5 µ C charge?
Chapter 20Static Electricity
-
-
-.03 m
.04 m -
F2
F1
Chapter 20Static Electricity
2
66229
1 )03(.
)105.4)(101.2)(/109(
m
CxCxCmNxF
F2 = 30 N
F1 = 95 N -
F2
F1
2
66229
2 )04(.
)105.4)(102.1)(/109(
m
CxCxCmNxF
Chapter 20Static Electricity
F2 = (30 N)2+ (95 N)2 = 9736
F = 99 N
tan = 30 N/ 95 N = .315
= 17°
The force on the 4.5 µC is 99 N at 343º
-
30 N
95 N
φ