Name ____________________________________Electric Fields

Go to http://phet.colorado.edu/simulations/sims.php?sim=Electric_Field_Hockey

and click on Run Now.

1. You rub balloons in your hair and then hang them like in the picture below. Explain why you think they move apart and what might affect how far apart they get. A balloon becomes negatively charged when it is rubbed on a person’s hair. This occurs because all the protons and neutrons leave the balloon and attach to other objects such as the hair. If two balloons both have negative charges then both balloons will repel each other because same charges repel while opposites attract.

2. Test your ideas using Electric Field Hockey in the Practice mode. Make a table to record your observations about what affects the direction and speed of the puck. Your table should demonstrate that you have run controlled tests with all the variables.

...SACE Stage 2 Physics
ElectricFields 1 Solution
1. (a) State Coulomb's Law.
Any two point charges have acting on them equal sized oppositely directed forces acting along the line joining their centres. The magnitude of these equal sized forces is directly proportional to the product of the charges and inversely proportional to the square of their distance apart. The forces are attractive for unlike charges and repulsive for like charges.
[pic].
e.g.
(b) Find the electrostatic force between charges of +2.0 C and +5.0 C separated by a distance of 75 m in a vacuum.
q1 = 2.0 C q2 = 5.0 C r = 75 m
[pic]
[pic]
2 Two charges of +8.0 mC and -6.0 mC attract each other with a force of 3.0 x 103 N in a vacuum. What is the distance between the charges?
q1 = 8 x 10-3 C q2 = -6 x 10-3 C
F = 3 x 10 3 N
[pic]
[pic]
[pic]
3 A metal sphere of mass 6.0 x 10-3 kg is found to just float in air above a similar metal sphere when both have a charge of 4.0 mC. Assuming that the only upwards force is electrostatic repulsion, find the distance between the spheres.
M = 6.x 10-3 kg g = 9.8 ms-2 q1 = 4 mC
q2 = 4 mC (Could both be + or - charges)
Forces acting have equal magnitudes, opposite directions
Fcoulombic = Fgravitational
Since the gravitaional force is equal and...

...Name ____________________ ElectricFields
Go to http://phet.colorado.edu/simulations/sims.php?sim=Electric_Field_Hockey
and click on Run Now.
1. You rub balloons in your hair and then hang them like in the picture below. Explain why you think they move apart and what might affect how far apart they get.
They move apart because they become charged while you are rubbing them in your hair and the charges are the same on both balloons. The more charges you get on the balloon the further away they will move from one another because the charges will be stronger and they will repel more strongly and rapidly.
2. Test your ideas using ElectricField Hockey in the Practice mode. Make a table to record your observations about what affects the direction and speed of the puck. Your table should demonstrate that you have run controlled tests with all the variables.
First it depends if the puck is a positive or negative charge that determines whether it will be attracted to or repelled from the positive and negative balls. It also depends on the mass of the puck the smaller the mass the faster the puck moves. Another variable is how many charges you have near the puck the more you have in a straight line the quicker it attracts or repels. It also depends where you put the charged balls around the puck to determine which direction it goes.
3. Reflect on your ideas from question #1 and your data...

...navigation, search
Electromagnetism is the physics of the electromagnetic field, a field that exerts a force on particles with the property of electric charge and is reciprocally affected by the presence and motion of such particles.
A changing magnetic field produces an electricfield (this is the phenomenon of electromagnetic induction, the basis of operation for electrical generators, induction motors, and transformers). Similarly, a changing electricfield generates a magnetic field.
The magnetic field is produced by the motion of electric charges, i.e., electric current. The magnetic field causes the magnetic force associated with magnets.
The theoretical implications of electromagnetism led to the development of special relativity by Albert Einstein in 1905; and from this it was shown that magnetic fields and electricfields are convertible with relative motion as a four vector and this led to their unification as electromagnetism.
See also: history of electromagnetism and Magnetism
While preparing for an evening lecture on 21 April 1820, Hans Christian Ørsted developed an experiment that provided surprising evidence. As he was setting up his materials, he noticed a compass needle deflected from magnetic north when the...

...Electric Charge and ElectricField:->
1. Electric Charge
Electric charge is a fundamental property like mass, length etc associated with elementary particles for example electron, proton and many more.
Electric charge is the property responsible for electric forces which acts between nucleus and electron to bind the atom together.
Charges are of two kinds
(i) negative charge
(ii) positive charge
Electrons are negatively charged particles and protons, of which nucleus is made of, are positively charged particles. Actually nucleus is made of protons and neutrons but neutrons are uncharged particles.
electric force between two electrons is same as electric force between two protons kept at same distance apart i. e., both set repel each other but electric force between an electron and proton placed at same distance apart is not repulsive but attractive in nature.
Conclusion
(a) Like charges repel each other
(b) Unlike charges attract each other
Assignment of negative charge on electron and positive charge on proton is purely conventional , it does not mean that charge on electron is less than that on proton.
Importance of electric forces is that it encompasses almost each and every field associated with our life; being it matter made up of atoms or molecules in which...

...Chapter One
ELECTRIC CHARGES
AND FIELDS
1.1 INTRODUCTION
All of us have the experience of seeing a spark or hearing a crackle when
we take off our synthetic clothes or sweater, particularly in dry weather.
This is almost inevitable with ladies garments like a polyester saree. Have
you ever tried to find any explanation for this phenomenon? Another
common example of electric discharge is the lightning that we see in the
sky during thunderstorms. We also experience a sensation of an electric
shock either while opening the door of a car or holding the iron bar of a
bus after sliding from our seat. The reason for these experiences is
discharge of electric charges through our body, which were accumulated
due to rubbing of insulating surfaces. You might have also heard that
this is due to generation of static electricity. This is precisely the topic we
are going to discuss in this and the next chapter. Static means anything
that does not move or change with time. Electrostatics deals with the
study of forces, fields and potentials arising from static charges.
1.2 ELECTRIC CHARGE
Historically the credit of discovery of the fact that amber rubbed with
wool or silk cloth attracts light objects goes to Thales of Miletus, Greece,
around 600 BC. The name electricity is coined from the Greek word
elektron meaning amber. Many such pairs of materials were known...

...HW 1 solutions Point Charge in One Dimension
A point charge q1 = -3.5 μC is located at the origin of a co-ordinate system. Another point charge q2 = 5.1 μC is located along the x-axis at a distance x2 = 9.3 cm from q1. 1) What is F12,x, the value of the x-component of the force that q1 exerts on q2?
-18.57
N
For all of these problems we want to make use of the standard electric force equation: ̂ So for this problem with K=9*109 Nm2/C2, Q1=-3.5μC, Q2=5.1 μC, and r=9.3 cm we get F=-18.57 N. It’s important to realize that getting a negative force value means the charges attract. The direction of that attraction is determined by which charge we’re looking at.
2) Charge q2 is now displaced a distance y2 = 2.7 cm in the positive y-direction. What is the new value for the xcomponent of the force that q1 exerts on q2?
-16.45
N
Same idea as 1 but with a different r. We use the Pythagorean theorem to find the new distance which is 9.684 cm. Using the force equation again we get F=-16.45
3) A third point charge q3 is now positioned halfway between q1 and q2. The net force on q2 now has a magnitude of F2,net = 5.71 N and points away from q1 and q3. What is the value (sign and magnitude) of the charge q3?
1.167
μC
Here since all the charges are on a line we don’t have to worry about different directions. We had to calculate the force on Q2 do to Q1 for our earlier problems which was -17.13. Since we know the total force we can just say...

...density
l
forms a circle of radius b that lies in the
xy-plane in air with its center at the origin.
a) Find the electricfield intensity E at the point (0, 0, h).
b) At what value of h will E in part (a) be a maximum? What is this maximum?
3. Determine the work done in carrying a
5 C charge from P1 ( 1, 2, 4) to
P2 (2, 8, 4) in the field E a x y a y x
a) along the parabola y 2x , and
2
b) along the straight line joining P and P2 .
1
4. A finite line charge of length L carrying uniform line charge density
l
is coincident
with x-axis.
a) Determine V in the plane bisecting the line charge.
b) Determine E from
l
directly by applying Coulomb’s law.
5. The polarization in a dielectric cube of side L centered at the origin is given by
P P0 (a x x a y y a z z ) .
a) Determine the surface and volume bound-charge densities.
b) Show that the total bound charge is zero.
6. The space between a parallel-plate capacitor of area S is filled with a dielectric
whose permittivity varies linearly from
1
at one plate (y=0) to
2
at the other plate
(y=d). Neglecting fringing effect, find the capacitance.
7. Three capacitors
1 C , 2 C , and 3 C are connected as shown in Figure across a
240-volt source. Calculate the electric energy stored in each capacitor.
1F
2 F
3F
+
-...

...
THE RELATIONSHIP OF ELECTRICFIELD INTENSITY AND ITS DISTANCE FROM THE CHARGED OPOINT
PHYS-232
JIANSONG HE
GROUP:
Abstract
This experiment was performed to find the electricfield strength from different distance to the charged point. The field strength was determined statically, by measuring its electrical potential when subjected to loading, and dynamically, by measuring the electrical potential at different location on the conductive paper. The electrical potential was measured from three different points for each positive charge and negative one.
Introduction
The objective of this research performed is to explore the relationship between electrical field strength and the distance from the charge. This research should fulfill Gauss’s law, which also known as Gauss's flux theorem, is a law relating the distribution of electric charge to the resulting electricfield.
The law was formulated by Carl Friedrich Gauss in 1835, but was not published until 1867. It is one of the four Maxwell's equations which form the basis of classical electrodynamics, the other three being Gauss's law for magnetism, Faraday's law of induction, and Ampère's law with Maxwell's correction. Gauss's law can be used to derive Coulomb's law, and vice versa.
This experiment also designed to determine if the electricfield and the...