3Q General Physics 2 PDF

notes by des :) ​ Positive Charge - Due to electron (-) deficiency 3Q GENERAL PHYSICS 2 ​ Negative Charge - Due to excess of...

notes by des :) ​ Positive Charge - Due to electron (-) deficiency 3Q GENERAL PHYSICS 2 ​ Negative Charge - Due to excess of electrons (-) LESSON 1: ELECTROSTATICS ​ These are caused by an external force or process known as CHARGING. Electricity Basic Unit of a Charge ​ A form of energy resulting from the ​ Coulomb or “C” where 1C = 6.25 x 10^18, existence of charged particles (such as and electrons or protons which are electrons or protons), either statically as stored in a dielectric. an accumulation of charge or ​ 1e = 1.60 x 10^-19C dynamically as a current. ​ Symbols for electric charge are Q or q. Electric Charge Properties of Charge ​ Imbalance in a substance between the 1.​ The Law of Conservation of Charge number of protons and electrons ​ Charges cannot be created nor ​ Two components of an electric charge in destroyed but can be transferred from an atom are protons (+) and electrons one material to another. The total (-). charge in a system must remain constant. Bohr Model of the Atom (Cu) ​ Electric Force - the attractive or repulsive force felt by a charge ​ An uncharged or neutral object that has balanced positive and negative charges cannot experience this force. 2.​ Electrostatic Law ​ Like charges repel and unlike charges attract. Conductors vs. Insulators Types of Charges Conductors ​ Electrons move easily from one atom to another ​ Permits charges to flow freely within it ​ Allow charges to be distributed evenly on its surface  ​ Examples: Copper, silver, gold object. The presence of a charged object will polarize the charge within the Insulators conductor. ​ Electrons stay in their orbits ​ Electroscope - Induction using an ​ Hinder the free flow charges within it Electroscope. ​ Charge is seldom distributed evenly ○​ An electroscope is used to across the surface of an insulator. determine the charge of ​ Examples: glass, rubber, plastic materials ​ Discharging - The process of removing Methods of Charging excess charges on an object is called discharging. 1.​ Charging by Conduction ○​ Grounding - When discharging is ​ When an uncharged body is brought done by means of providing a into contact (touched) with a charged path between the charged object body then the charge or electrons are and a ground. transferred from the charged body to ○​ Ground - Any object that can the uncharged body. This charges the serve as an “unlimited” source of uncharged body. electrons. ​ An object that exhibits electric interaction after rubbing is said to be Charge charged. ​ Polarization ○​ Electrostatic Polarization - A phenomenon where the charges within the neutral object are rearranged/separated such that the charged object attracts the opposite charges within the neutral object. ​ Lightning ○​ The negative charges at the bottom of the thunderclouds can cause the separation of charges on Earth. LESSON 2: COULOMB’S LAW 2.​ Charging by Induction Electric Force ​ A charged object is brought near but ​ Like charges: Repel; not touched to a neutral conducting ​ Unlike charges: Attract.  ​ Just as masses attract each other with gravity, charges exert forces on one another. However, charges can attract or repel depending on their type (positive or negative). ​ Gravitational force is only an attractive force. ​ Gravitational force is much weaker than Limitations the electric force. ​ Coulomb’s Law applies to point charges or spherically symmetric charge Coulomb’s Law ​ Coulomb’s Law calculates the magnitude of force F between two point charges, q1 and q2, separated by a distance r. In SI units, the constant K. distributions ​ This force works in a vacuum and real-world effects (like medium) modify ​ Greater force: shorter distance; it. ​ Weaker force: longer distance. Superposition Principle ​ Superposition principle states that the sum of forces on each charge is the vector sum of all the contributory forces of all the individual forces. ​ System of Point Charges  ​ It causes any charged particle placed in it to experience an electric force. ​ An electric field line is a curve in space, such that a tangent to any point of the line represents the direction of the electric field vector at that specific point. ​ The concept of an electric field is identifiable to the inclusion of a test charge on a certain region, where the effect of the field line is to be calculated. ​ The electric field is represented by the equation below: LESSON 3: ELECTRIC FIELD AND FLUX Electric Field ​ Just as a gravitational field represents the pull of gravity around a mass, an electric field represents the influence of a charge on other charges nearby. ​ If you’ve ever felt your hair stand up near a charged balloon, that’s an example of an electric field acting on charges in your hair. ​ Electric field is the space surrounding a charged body. ​ It is an imaginary field that helps ​ If q is positive, the direction of E is the explain the interaction between charged direction of F. On the other hand, the particles. force on a negative charge is opposite ​ Every charge has an electric field to the direction of the E. associated with it. Electric Flux ​ Electric flux, the product of electric field and the area of the surface projected in a place perpendicular to the field, can be defined by considering the area in question.  ​ Gauss' Law was formulated by the flow through the wire? (b) How many German scientist John Carl Friedrich electrons flow through the wire over the Gauss, as an alternative to Coulomb's given time interval? law. ​ Gauss' law states that the total electric I = 2.0 A flux through the closed surface is equal T - 16.0s to the net electric charge inside the surface, divided by the constant of the (a) Using Eq. (1), derive and solve for q. permittivity of free space. Q = It = (2.0 A)(16.0s) = 32 C (b) Recall that the charge of the electron is −1.602 × 10−19 C. Use a dimensional analysis to solve for the number of electrons flown LESSON 4: CIRCUITS over the given time, ​ If there is a source of water, and there is a pump, the water will start flowing due to pressure, causing the shaft to rotate. = 1.997503121 × 10^20 ​ Source → wire → load (light bulb) = 2.0 × 10^20 electrons Electric Current Resistors ​ Electric current (I) or simply current, is the amount of charge passing through any point in a conductor per unit time. I = q/t ​ The unit of current is coulomb/second (C/s) = ampere (A). 1A = 1C/1s ​ André Marie Ampère - considered to be “the Isaac Newton of electricity.” ​ Electrodynamics - the study of charges in motion. ​ Conventional current - normal way of reading a current. ​ Circuits were labeled with the current flowing from the positive terminal to the negative terminal of a source of voltage. ​ Always start in the positive (conventional) and not in the negative (electron). ​ Silver and Gold are the common colors Problem #1: for the tolerance of the resistor. A steady current of 2.0 A flows in a wire for 16.0 s. (a) How many coulombs of charge  ​ 1st digit - 1st color; 2nd digit - 2nd color; 3rd digit - multiplier; 4th digit - 4.​ Temperature tolerance. ​ Resistance R and resistivity ρ vary with ​ Black, Brown, ROYGBV, Grey, White temperature. As temperature increases, resistance and resistivity increase for conductors and decrease for insulators Example #1: and semiconductors. What is the resistance and temperature coefficient of resistance of a resistor if its color code is red-violet-yellow-black-gold? R = ρL/A Resistance of the resistor ρ = resistivity constant (R) = 274 x 1Ω ±5% L = length A = cross-sectional area If brown-red-green-gold: 12 x 10^5 Ω ± 5% Voltage = 1,200,000 Ω ± 5% ​ Voltage (V) or describes the “pressure” that pushes electricity. Factors Affecting the Resistance of a ​ The amount of voltage is indicated by a Uniform Wire unit known as the volt (V) ​ Higher voltages cause more electricity 1.​ Cross-Sectional Area to flow to an electronic device. ​ Resistance R varies inversely from the cross-sectional area A of the wire. As Ohmic Resistance the area increases, the resistance ​ Resistance is also defined as the ratio of decreases. voltage to the resulting current. ​ The wider the area of the wire, the lesser the resistance as there are more Ohm’s Law: R = constant = V/I electrons flowing through a wire. or R = voltage/current = V/I 2.​ Length ​ Voltage is directly proportional to ​ The resistance R of the wire is directly current wherein as the voltage proportional to its length L. A longer increases, the current increases. wire has greater resistance than a ​ Resistance is inversely proportional to shorter wire of the same material and the current whereas the voltage cross-sectional area. increases, the current decreases. ​ Longer wire has a greater resistance. ​ Charges eventually lose energy as they travel distances. 3.​ Material of the Wire ​ The effect of the kind of material on the resistance of the wire is determined by its resistivity ρ. Resistivity is the reciprocal of conductivity. Schematic Diagram of Circuit Elements ​ When two or more resistances or loads are present in a circuit—also called multiple loads. Parallel Circuits ​ Voltage is constant. ​ In a parallel circuit, the more resistors, the lesser is its total resistance.