Quick Write What are the different parts of a wave? What are the different properties of a wave? What are the parts of an atom? Copy the new set of equations. “Coulombs Law”

Quick Write Differentiate conductor from an insulator. What are the parts of an atom? How does a Van De Graaff Generator work? Differentiate the two types of charging.

Electrostatics

Electrostatics Defined as the study of electricity at rest. This does not mean that the electrons are not moving- it means that the bodies that carry the electrons that are usually at rest. Electrons are in perpetual motion.

Structure of the Atom Neutron Proton Electron Energy Levels or Orbits

Electric Forces and Charges

Like Signs Repel

Unlike Signs Attract

Electrical Force Woman is touching negatively-charge sphere Electrical force is more powerful than gravity

Conservation of Charge

Charge Electrons and protons have an attribute called charge Electrons have a negative charge Protons have a positive charge

Charge Conservation Charge is neither created or destroyed. What we call charging is either Transfer of charges, or Internal rearrangement of charge carrying units

Removing Electrons from Atoms Rubber scrapes electrons from fur atoms

Charles Augustin Coulomb (1736 - 1806) Coulomb’s Law Charles Augustin Coulomb (1736 - 1806) F = k q1q2 / d2 q = charge in Coulombs k = 9 x 109 N-m2/C2 d = distance in m Compare this to the gravitational force law: F = G m1m2 / d2

Coulomb’s Law States that the force of attraction or repulsion between two small charged bodies is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them. One Coulomb = 6.25 x 1018 electrons Proton charge = +1.6 x 10-19 C Electron charge = - 1.6 x 10-19 C

What happens to the magnitude of the force as the charges get farther apart?

Conductors An electrical conductor is a substance through which electrical current flows with small resistance Metals are generally excellent electrical conductors The electrons in conductors lie in an ‘loose’ outer orbit – the so-called "valence band"

Insulators An electrical insulator is a substance with an extremely high resistance to the flow of charge Most nonmetals solids are generally excellent insulators Most atoms hold on to their electrons tightly and are insulators

Net Charge Neutral

Net Charge Positive

Net Charge Negative

Charging by Touching

Charging by Induction

Neutral Objects are Attracted to Charged Objects Charged comb attracts neutral bits of paper

Lightning, lightning rods Charge Distributions Charge on Metals                             Metal Ball Charge on Metal Points                                   Lightning, lightning rods

Electroscope Conductor Insulator Metal Leaves

Coulomb’s Law States that the force of attraction or repulsion between two small charged bodies is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them. One Coulomb = 6.25 x 1018 electrons F = k q1 q2 / d2

8 6 6 8 7 7

9 -6 -6 9 ? ?

-4 10 10 -4 ? ?

Sample Problem 1 Two objects exert an electric force of size F on each other. If the charge on each object is doubled, the electric force will now be ____ ¼ F F 2F 4F

Sample Problem 2 Two objects exert an electric force of size F on each other. if the objects are moved three times closer together (so d is being reduced) the electric force will now be ____ 1/3 F 3F 1/9 F 9 F

Sample Problem 3 Two objects exert an electric force size F on each other. If the charge on each object is doubled and they are moved three times closer together, the electric force will now be ____ 36 F 18 F 12 F ¾ F

Sample Problem 4 What is the magnitude and direction of the force on a charge +4 x 10-9 C that is 5 cm from a charge of +5 x 10-8 C? Two charges are separated by 3 cm. Object A has a charge of +6 uC, while object B has a charge of +3 uC. What is the force on object A? Is it attractive or repulsive and in what direction?

Sample Problem 5 A negative charge of -2 x 10-4 C and a positive charge of 8 x 10-4 C are separated by a 0.30 m. What is the force between 2 charges? Two electrons in an atom are separated by 1.5 x 10-10 m. What is the electrical force between them? A positive and a negative charge, each of magnitude 1.5 x 10-5 C, are separated by a distance of 15 cm. Find the force on each of the particles.

Try… 2 negatively charged bodies, each charged with -5 x 10-5 C, are 0.20 m from each other. What force acts on each other? Two objects exert an electric force of size F on each other. if the objects are moved three times closer together (so d is being reduced) the electric force will now be ____ Two charges are separated by 6 cm. Object A has a charge of +8 uC, while object B has a charge of +4 uC. What is the force on object A? Is it attractive or repulsive and in what direction?

Sample Problem 6 with Vector A sphere with charge 6 C is located near two other charged spheres. A -3 C sphere is located 4 cm to the right and a 1.5 C is located 3 cm to the left. Determine the net force on the 6 C sphere. A positive charge of 3 uC is pulled on by two negative charges. One, -2 uC is 0.05 m to the north and the other, -4 uC, is 0.30m to the south. What total force is exerted on the positive charge?

Sample Problem 6b Three particles are placed on a straight line. The left particle has a charge of +4.6 x 10-6 C, the middle particle has a charge of -2.3 x 10-6 C, and the right particle has a charge of -2.3 x 10-6 C. The left particle is 12 cm from the middle particle and the right particle is 24 cm from the middle. Find the total force on the middle particle.

Try… A positive charge of 6 C is pulled on by two negative charges. One, -2C is 0.60m to the north and the other -5C is 0.70m to the south. What total force is exerted on the positive charge? A negative charge of 6 x 104 C is at the center of two negative charges. One, -3x106 C, 0.40 m to its right and -4x106 C, 0.30m to its left. What is the resultant force in the middle charge?

E = F / q Electric Field Michael Faraday A charge creates an electric field about it in all directions. E = F / q

Problem Solving 1 A negative charge of 2 x 10-8 C experiences a force of 0.60 N to the right in an electric field. What are the field magnitude and direction? A positive test charge of 5 x 10-4 C is in an electric field that exerts a force of 2.5 x 10-4 N on it. What is the magnitude of the electric field at the location of the test charge?

Problem Set 2 A positive charge of 1 x 10-5 C experiences a force of 0.20 N when located at a certain point. What is the electric field intensity at that point? A positive test charge of 8 x 10-5 C is placed in an electric field of 50 N/C intensity. What is the strength of the force exerted on the test charge?

Electric Potential Difference V = W / q Defined as the work done moving a test charge in an electric field divided by the magnitude of the test charge. Measured in J/C or 1 Volt Electric Potential is SMALLER when two unlike charges are closer and LARGER when two like charges are closer together.

Uniform Field V = Ed d = distance (m) V = Potential Difference (volt) E = Electric Field (N/C)

Sample Problem 1 Two parallel plates are given opposite charges. A voltmeter measures the electric potential difference to be 60V. The plates are 3 cm apart. What is the magnitude of the electric field between them? The electric field intensity between two large charge parallel metal plates is 8000 N/C. The plates are 0.05m apart. What is the electric potential difference between them?

Sample Problem 2 A voltmeter reads 500 V across two charged parallel plates that are 0.020m apart. What is the electric field between them? What electric potential difference is applied to two metal plates 0.500m apart if the electric field between them is 2.5 x 103 N/C. What work is done when 5C is moved through an electric potential difference of 1.5 V?

Try… Two large charged parallel plates are 0.40 m apart . The magnitude of the electric plates between the plates is 625 N/C. a. What is the electric potential difference between the plates? b. What work will you do to move a charge equal to that of one proton from the negative to the positive plate?

C = q/ V Capacitance measure in Farads (F) Stored charge in a capacitor.

Sample Problem 1 A sphere has an electric potential difference between it and Earth of 60 V when it has been charges to 3 x 10-6 C. What is its capacitance? A 27 F capacitor has an electric potential difference of 25V across it. What is the charge on the capacitor? Both a 3.3 F and a 6.8 F capacitor are connected across 15V electric potential difference. Which capacitor has a greater charge? What is it?

Quick Write Two charges are separated by 6 cm. Object A has a charge of +8 uC, while object B has a charge of +4 uC. What is the force on object A? Is it attractive or repulsive and in what direction? 2 negatively charged bodies, each charged with -5 x 10-5 C, are 0.20 m from each other. What force acts on each other?

Try… Two large charged parallel plates are 0.40 m apart . The magnitude of the electric field between the plates is 625 N/C. a. What is the electric potential difference between the plates? b. What work will you do to move a charge equal to that of one proton from the negative to the positive plate?

Bonus Arnold Schwarzenegger has a big one Michael j fox has a small one Madonna doesn't have one the pope has one but he never uses it Bill Clinton Has one and he uses it all the time! What is it?...