Charges
What are the two types of electric charge and what are their respective values?
Electron (-1.602 x 10-19 C) and Proton (+1.602 x 10-19 C)
When silk and glass are rubbed together, why does the glass become positive and the silk become negative
Electrons leave an atom whose outer shell is almost empty and are attached to an atom whose outer shell is almost full. Therefore, electrons are moved from the almost empty outer shell of atoms in glass to the almost full outer shell of atoms in silk. Determining this transfer can easily be done with the help of an affinity table.
Upon what factors does the electrical force between two charged objects depend? What formula relates these factors?
Charge of each object and the distance between them.
F = (kqq1q2)/r2
What is an electric field? What is meant by the electric field strength? What are the units of the electric field strength?
region in space surrounding a charged object in which another charged object experiences an electrical force.
A measure of the strength of the electric force felt by a positive test charge in an electric field.
N/C
A test point with a charge of 8.6 x 10-17 C experiences a force of 5.5 x 10-7 N when placed in an electric field. Find the electric field strength at that point.
6.4 x 1011 N/C
What is the Basic Law of Electrostatics?
Like charges repel, and unlike charges attract.
Why are some materials good conductors and other good insulators?
Conductors allow electrons to move freely, and insulators don't allow electrons to move freely. The valence electrons in conductors to transfer easily, while the valence electrons in insulators are heavily bound to the nucleus.
What type of force is an electrical force?
Field Force
What are the four properties of Electric Field lines?
1. Electric field lines originate from a positively charged object and terminate at a negatively charged object.
2. Electric field lines originate and terminate perpendicular to the surface of a charged object.
3. The density of the electric field lines indicate the strength of the electric field.
4. No two field lines from the same source can cross.
Find the electric field strength of the field generated by an object with a charge 385 µC at a distance of .350 m.
2.82 x 107 N/C
What experiment is attributed with quantifying the charge of an electron and charge of a proton?
Millikan Oil Drop Experiment
What does it mean for an isolated conductor to become charged by conduction?; by induction?
Conduction: Comes into contact and electrons are permanently transferred.
Induction: No contact and electrons are temporarily moved to one side of the conductor creating a temporary positive or negative net charge.
Which is greater between 2 electrons: Gravitational Field force or Electric Field force? By how much?
Electric Field Force: Approximately 1042 times greater (approximately 1000000000000000000000000000000000000000000 times greater)
Draw the electric field for a system of 2 charges separated by a distance, d, with equal but opposite charges, +q and -q. +q is right of -q.
(Will draw on board)
At what distance will the force between 2 protons be 3.25 x 10-14 N ?
8.42 x 10-8 m
What does it mean for an object to be grounded?
The object has no net charge.
Compare the residual charge left on a conductor by conduction; by induction.
Conduction: The conductor gains residual charge from the material until they both have the same charge.
Induction: No contact is made, so no residual charge is left.
Two particles with charges of -38 nC and 65 nC are 680 mm apart. Find the magnitude of the electrical force between them. Is it a force of attraction or repulsion?
4.8 x 10-5 N
Attraction
List the four properties of isolated charged conductors.
1. The electric field is zero everywhere inside the conductor.
2. All excess electric charge lies on the outer surface.
3. The electric field is perpendicular to the conductor’s surface.
4. On an irregular shaped conductor, charge accumulates at the point(s) of greatest curvature.
Q1 (150 µC) and Q2 are separated by 155 cm. A third charge, Q3 (250 µC) is placed between Q1 and Q2 at a distance of 64 cm away from Q1. Q3 is in electrostatic equilibrium. What is the charge on Q2?
3.0 x 10-4 C
A charged object has a net charge of -8.01 nC. How many more electrons than protons does the object have?
If the object has 6.50 x 1011 protons, how many total electrons are there?
5.00 x 1010 electrons
1.150 x 1011 electrons
A conducting sphere with a net charge of 10.0 x 10-8 C comes into contact with a conducting sphere with a net charge of 4.0 x 10-7 C. What is the net charge on each sphere after they come into contact?
7.0 x 10-8 C
Q1 (6.0 µC) is 0.55 m North of Q2 (8.0 µC). Q1 is 45 cm East of Q3 (7.0 µC). Find the net force on Q1.
2.3 N at 53 degrees E of N
or
2.3 N at 37 degrees N of E
At what distance would an object with a charge of 350,000,000 nC generate an electric field with a strength of 9.5 N/C?
18000 m
Three point charges lies along the x axis at x=0, x= 75 mm and x = 198 mm. The 1st charge is 7.0 µC, the 2nd is -8.0 µC, and the 3rd is -6.5 µC. Calculate the magnitude and direction of the electrical force on each charge.
F1 = +99 N
F2 = -1.20 x 102 N
F3 = +21 N