A document discusses conductors, capacitors, dielectrics, electric fields and forces, important concepts in electricity including circuits, capacitors, and formulas. Key points include: - Conductors allow free movement of electrons while dielectrics are electrical insulators. - Electric fields exist around charged objects and point in the direction of force on a positive test charge. Capacitance depends on physical characteristics like plate area and separation. - Circuits can be series or parallel. Kirchhoff's rules are used to solve complex circuit problems regarding potential and current. - Capacitors store electric charge between conductors separated by a dielectric. They function to block DC and pass AC current.

1. Conductors, Capacitors, Dielectrics

2. Explanation of Conductors The electric wire must have the proper number of conductors Older two-wire electrical circuits, such as the two circuits depicted at the right of our sketch may provide only the hot and neutral wires and no ground wire. The electrical circuit wire must be properly routed and secured between the electrical panel and the receptacle location, and must be properly secured at the junction box that is to hold the electrical receptacle.

3. Main Concepts of Electric Forces and Fields Electric forces and electric fields are vectors, electric potentials are scalars Electric fields point in the direction of the force on a positive test charge Capacitance is the ratio of charge to the potential for a given conductor the plate seperation and the permittivity or dielectric constant of a system of parallel plates depends only on the physical characteristics of the capacitor (i.e. Surface area, plate seperation, dielectric material)

4. Dielectric Explanation A dielectric capacitor consists of two metal sheets placed on either side of a layer of dielectric material. Dielectrics are materials like glass or plastics (polymers) which are insulators. The behavior of a dielectric is determined by its dielectric constant value.

5. Important Vocabulary Electrostatics – is the study of interaction between electric charges which are not moving Conductors – are materials in which the electrons are free to move. Some examples such as silver, copper, gold, and mercury as metals Electric Fields – exist in the space surrounding a charged particle or object Capacitor- stores electric charge and consists of two conductors seperated by an insulator known as a dielectric Dielectric – is an electrical insulator that can be magnitize both electric charges by an applied electrical field Electric Current – is the rate of flow of electric charge. Used in Amperes (I) where 1 Ampere is 1 coulumb/second Electrical Resistance refers to the opposition offered by a substance to the flow of electrical current. Unit of resistance is Ohm

6. Capacitor Explanation A capacitor which is an energy-storage device is used to store energy between two conductors. These conductors are also called plates. An insulator is placed between these two plates. These plates are charged in order to store energy. One of the main function of a capacitor is to work as a filter. In this process blocks DC (Direct Current) and passes AC (Alternating Current).

7. Important Formulas Electric Charge: q = n e ; where e = 1.6 X 10-19 C; (q) is the total charge on an object, (e) is the fundmental unit of charge, (n) is the number of total charges Coulomb’s Law: F = k Q1 Q2/r2 ; where k = 9 X 109 N m2 /C2 ; (F) is the two charges exerted a force (Q) is the magnitude of the charge while (r) is the squared distance of charge

8. Important Formulas # 2 Electric Field: E = F/q or F = q E ; (E) is the magnitude of electric field, (F) force exerted om test charges, (q) is the magnittude of the charge of test particle Electric Field to a Point Charge: E = k Q /r2 ; (E) is the magnitude of electric field, (F) force exerted om test charges, and (r) is the distance from the charge

9. Important Formulas # 3 Electric Potential: V = PEa / q ; (PEa) is the potential energy, (q) per unit charge (V) is the electric potential at point Capacitance: C = Q/V ; (C) is the ratio of the charge stored, (Q) is the potential difference, (V) is between the conducting surfaces Electric Current: I = Q/t ; (I) is the electric current in Amperes Electrical Resistance: R = p L/A ; (R) is the resistance of metal wire, (L) length, (A) cross-sectional area, (p) is the resistivity Ohm’s Law: I = V/R or V = IR ; (I) stands for electric current and (V) stands for voltage of current and (R) stands for the resistivity

10. Electric Circuits

11. Main Concepts An electrical network with a closed path Measured in terms of number of charge carriers or Particles containing an unit electric charge The current flows through a resistance

12. Circuits Series Circuit - is an electric field with only a single path for electric current to travel. The current through each circuit is the same. Parallel Circuit - is an electric circuit with more than one path fore electric current to travel. The current is divided among the branches of the circuit. The voltage drop is the same across each branch.

13. Kirchhoff’s Rules Used in junction with Ohm’s law in solving problems involving complex circuits All junctions in a circuit have the same potential The sum of all the potentials around a closed loop is zero The sum of all the currents around a closed loop is zero The sum of the charges stored at all junctions in a closed loop of a circuit is zero

14. RC Circuits/Kirchhoff’s Rules # 2 RC Circuit - consists of a resistor and a capacitor connected in series to a DC Power source. First Rule or Junction rule The sum of all currents entering any junction point equals the sum of all currents leaving the junction point. Based on the law of conservation of electric charge Second Rule or Loop Rule The algebraic sum of all the gains and losses of potential around any closed path must equal zero. Based on the law of conservation of energy

15. Suggestion for Using Assign a direction to the current in each individual branch of the circuit - Positive on each side of resistor where current enters, negative sign on the side where current exits

16. Tips to help you out Things to Think About

17. DC Circuits Draw an illustration correctly labeling everything before beginning Check to make sure you have assigned the proper signs to potential differences when using Kirchhoff’s rules With Kirchhoff’s rules, you guess the directions of the currents (if correct, positive; incorrect, negative) Capacitors in DC Circuits are circuit disrupters, meaning no current across the plane Ammeters are connected in series with the resistance and voltmeters are connected parallel to them

18. Electric Currents Make sure not to confuse resistance with resistivity Make sure to calculate cross-sectional area and correctly convert cm squared to m squared Remember how to calculate the power dissipated in a resistor

19. Capacitance Electrical potential is a property of space Potential energy: a property assigned to a charge Potential difference & difference in potential energy is not the same Potential is zero at great distance from a charge

20. Electric Fields For our purposes, an object cannot be affected by its own field The direction of electric field is the direction of the force the field exerts on a positive charge or the direction of electric field is the same as the direction from high potential to low potential For the motion of a charged particle in an electric field, use the system of equations for constant acceleration that we use for projectiles

21. Practice Problems

22. Electric Currents A) Determine the electrical resistance of a 20.0 m length of tungsten wire of radius of 0.200 mm B) If the temperature of the wire does not change, determine the resistance of the same wire if it is stretched to a length of 60.0 m. The resistivity of tungsten is 5.60 x 10-3 (symbol) m.

23. Electric Currents Contin. An electric immersion heated rated at 250 watts is inserted in a 100 gram aluminum cup which contains 200 grams of water. Initial temp of cup and water: 20.0 degrees C Determine the time required for the temperature of the cup and water to rise to 90.o degrees C. **The specific heat of aluminum is 0.220 cal/g C and water is 1.00 cal/g C

25. b) an ammeter which measures currents from 0-1.00A