Chapter 1 - Electric Charge & Electric Force PDF

CHECKPOINT: QUESTION 1. Which of the following particles is known to have a negative electric charge? A. Proton B. Neutron C. Electron D. Photon CHECKPOINT: QUESTION 1. Which of the following particles is known to have a negative electric charge? A. Proton...

CHECKPOINT: QUESTION 1. Which of the following particles is known to have a negative electric charge? A. Proton B. Neutron C. Electron D. Photon CHECKPOINT: QUESTION 1. Which of the following particles is known to have a negative electric charge? A. Proton B. Neutron C. Electron D. Photon CHECKPOINT: QUESTION 2. What is the SI unit of electric charge? A. Ampere (A) B. Volt (V) C. Coulomb (C) D. Ohm (Ω) CHECKPOINT: QUESTION 3. When two objects have the same charge, they: A. Attract each other B. Repel each other C. Remain unaffected D. Create a magnetic field CHECKPOINT: QUESTION 4. The process of transferring electric charge by direct contact between materials is known as: A. Induction B. Conduction C. Polarization D. Friction The foundation of electricity → ELECTRIC CHARGE WHY ELECTRICITY IS SO IMPORTANT TO US???  WHY ELECTRICITY IS SO IMPORTANT TO US??? Trains, electronic gadgets, heating and cooling appliances, and many more, even our brain uses electricity to work ELECTRICITY is a phenomenon associated with stationary or moving electric charges. CHAPTER 1: ELECTRIC CHARGE & ELECTRIC FORCE  A BRIEF HISTORY OF ELECTRIC CHARGE amber can attract nearby objects when rubbed with cloth Thales of Melitus 600 BC  A BRIEF HISTORY OF ELECTRIC CHARGE Thales of Melitus 600 BC 1600s William Gilbert Other substances demonstrated the same ability of amber substances attracted to amber = electrics ability of amber to attract = electricity (Greek: “elektron” means “amber”  A BRIEF HISTORY OF ELECTRIC CHARGE There are two types of electricity Positive and Negative Thales of Melitus Benjamin Franklin 600 BC 18th century 1600s William Gilbert ELECTRIC CHARGE a fundamental property of matter carried by subatomic particles which governs how subatomic particles are affected by electromagnetic field PROTON – positive charge (Ernest Rutherford) ELECTRON – negative charge (J.J. Thomson) MASS NEUTRON – chargeless (James Chadwick) The particles inside the nucleus are governed by a strong nuclear force → it requires a lot of energy to transfer proton & neutron The electrons can be easily transferred to another atom requiring small amount of energy  NEUTRAL ATOM POSITIVE ATOM NEGATIVE ATOM # of proton = # of electron # of proton > # of electron # of proton < # of electron 2 protons (2+) 2 protons (2+) 2 protons (2+) 2 electrons (2-) 1 electron (1-) 3 electrons (3-) ZERO NET CHARGE POSITIVE NET CHARGE NEGATIVE NET CHARGE CONSERVATION OF CHARGE The principle of conservation of charge states that, “charges can neither be created nor destroyed, they can only be transferred from one body to another” A net zero charge glass rod when rubbed with silk becomes a positive net charge, in effect, a net zero charge silk becomes a negative net charge QUANTIZATION OF CHARGE The quantization of charge states that, “charged objects can only exist in the form of the integral multiple of electron → electron as the smallest charge” In 1963, Gell-Mann & Zweig proposed the existence of quarks which carry fractional charges of atom QUANTIZATION OF CHARGE STANDARD MODEL OF PARTICLE CHECKPOINT: QUESTION 1. When two objects are rubbed together and one becomes positively charged, what happens to the other? A. It remains neutral B. It becomes negatively charged C. It loses mass D. It becomes positively charged CHECKPOINT: QUESTION 2. The quantization of charge means that charge: A. Can exist in fractional amounts B. Can only exist in integer multiples of a fundamental value C. Can be continuously divided into smaller parts D. Is not bound by specific numerical values CHECKPOINT: QUESTION 3. The elementary charge is the charge of: A. A proton B. An electron C. A neutron D. An alpha particle If objects are originally neutral, how do they become positive or negative charged objects? CHARGING BY FRICTION A charging process which is the results when two different materials are rubbed together When the glass rod and silk are rubbed together, the electron from the glass rod is transferred to the silk → friction creates energy, and that energy is used in transferring electrons positive net charge → glass rod negative net charge → silk Is it possible for the electrons of the silk to transfer to the glass rod?  CHARGING BY FRICTION TRIBOELECTRIC SERIES the ranking of materials based on their electron affinity when two different materials are rubbed together, the one that is higher on the list will become positively charged. CHECKPOINT: QUESTION When the comb run through human hair. What charge is acquired by the hair and by the comb? CHARGING BY FRICTION  TYPES OF MATERIALS (CONDUCTIVITY) CONDUCTOR material that permits electric charge to move easily from one region to another INSULATOR material that does not allow electric charge to flow SEMICONDUCTOR material that has an intermediate property of both conductor and insulator CHARGING BY CONDUCTION a charging process that requires a physical contact between a charging body and a neutral body. CHARGING BY INDUCTION a charging process where a neutral charged object can be charged without a direct contact with the charge object  CHECKPOINT: QUESTION 1. A positively charged rod is brought close to one end of a neutral metallic plate. What type of charge is induced on the farthest side of the plate? A. Positive B. Negative C. Neutral D. More information needed  CHECKPOINT: QUESTION 2. When a plastic cover is rubbed through hair, some hair are attracted in plastic cover after rubbing. What charge is acquired by the hair and the plastic cover? A. Hair - positive & Plastic cover - negative B. Hair - negative & Plastic cover - positive C. Hair - positive & Plastic cover - positive D. Hair - negative & Plastic cover - negative  CHECKPOINT: QUESTION 3. A positively charged rod is brought near a charged electroscope. As a result of doing this, the electroscope leaves move further apart. What is the charge on the electroscope? A. Positive B. Negative C. Neutral D. More information needed How do we know how strong (strength) the attraction or repulsion between two charged objects? ELECTRIC CHARGE Two unlike charges will always attract and two like charges will always repel just like a magnet CHECKPOINT: RECALL An electric charge or simply a charge is a physical quantity. What unit is used to measure the amount of electric charge a body possess? ELECTRIC CHARGE Electric charges can be represented by symbol (q) and the SI unit of electric charge is called Coulomb represented by C Charles-Agustin de Coulomb is a French engineer and physicist Coulomb found that each electric point charge exerts a mechanical force from each other 1 Coulomb = 6.25 x 10¹⁸ electrons 1 electron = -1.6 x 10⁻¹⁹ Coulombs 1 proton = 1.6 x 10⁻¹⁹ Coulombs COULOMB’S LAW the measurement of the strength of attraction or repulsion between two charged objects Coulomb discover the magnitudes of the electric forces between charged objects using the torsion balance, which he invented COULOMB’S LAW this law states that, “The magnitude of the electric force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them”  COULOMB’S LAW |𝒒𝟏 𝒒𝟐 | 𝑭=𝒌 𝒓𝟐 electric force between two-point electric force between two-point charges is directly proportional to charges is inversely proportional the product of the charges to the square of the distance between them 𝑭 𝜶 𝒒𝟏 𝒒𝟐 𝟏 ↑𝒓=↓𝑭 ↑ 𝒒𝟏 𝒒𝟐 = ↑ 𝑭 𝑭𝜶 𝟐 𝒓 ↓𝒓=↑𝑭 ↓ 𝒒𝟏 𝒒𝟐 = ↓ 𝑭 + - ++++ -- -- + - + - CHECKPOINT: QUESTION Is there a resemblance between electric force attraction/repulsion and romantic love attraction?  CHECKPOINT: SAMPLE PROBLEM In the Bohr model of Hydrogen atom, the proton and electron are separated by a distance of approximately 5.3x10⁻¹¹ m. Find the magnitudes of the electric force between two particles.  CHECKPOINT: SAMPLE PROBLEM Two point charges, 𝒒𝟏 = +25 nC and 𝒒𝟐 = -75 nC, are separated by a distance of 0.03 m. Find the magnitude of the electric force.  CHECKPOINT: SAMPLE PROBLEM Two point charges, 𝒒𝟏 = +25 nC and 𝒒𝟐 = -75 nC, are separated by a distance of 3.0 cm. Find the magnitude and direction of (a) the electric force that 𝒒𝟏 exerts on 𝒒𝟐 and (b) the electric force that 𝒒𝟐 exerts on 𝒒𝟏 CHAPTER 1: COULOMB’S LAW OBJECTIVES A. Define Coulomb's Law and identify the variables involved (charges, distance, and Coulomb's constant). B. Develop an appreciation in exploring real-world applications of Coulomb's Law in technology and everyday life. C. Solve problems related to Coulomb’s Law. CHECKPOINT: QUESTION 1. Which of the following factors does NOT affect the electrostatic force between two charged objects according to Coulomb's law? A. Magnitude of charges B. Distance between charges C. Mass of the objects D. Permittivity of the medium CHECKPOINT: QUESTION 2. According to Coulomb's law, what happens to the electrostatic force between two charges if the distance between them is doubled? A. It doubles B. It quadruples C. It halves D. It reduces to one-fourth CHECKPOINT: QUESTION 3. If the charges of two objects are doubled while the distance between them remains the same, how does the electrostatic force change? A. It doubles B. It quadruples C. It remains the same D. It is halved  CHECKPOINT: SAMPLE PROBLEM Two point charges located on the positive x-axis of a coordinate system. Charge 𝒒𝟏 = +1.0 nC is 2.0 cm from the origin and charge 𝒒𝟐 = -3.0 nC is 4.0 cm from the origin. What is the net force exerted on charge 𝒒𝟑 = +5.0 nC located at the origin?  CHECKPOINT: SAMPLE PROBLEM A +100 μC charge is placed at the origin. A -50 μC charge is placed at x= 2.0 m and a +200 μC is placed at x= -4.0 m. What is the net electric force acting on the +100 μC charge?  ACTIVITY #1: COULOMB’S LAW INSTRUCTIONS: Solve the following problems and use IGRESA format. Use 1 whole YELLOW paper. Copy & Answer. Box your final answer. 1. A negative charge of -197 μC and a positive charge of +765 μC are separated by a distance of 26 cm. Calculate the force between the two charges. 2. How apart are two charges, the charges are +3 μC and the other is +5 μC, if the force between them is 16 N? (Clue: Derive the equation) 3. Three charged particles are arranged in a line, as shown in the figure. Calculate the net electrostatic force on particle 3 due to the other two charges. 13 23 CHECKPOINT: ASSIGNMENT If there are two charges, a positive and a negative, how does each one know the other is there???