The electric, field has both a magnitude and a direction. whereas when the force is negative the charges attract each other. a) In Table C, Figure 4 of the data section, draw a distance vector triangle. K c is called Coulomb's Force Constant or Electrostatic Force Constant. Lab 3 Density Worksheet Completec. Objectives: 1-Satisfy Coulomb's law experimentally 2 . Mathematically, the magnitude of this electrostatic force F eacting on two charged particles (q1, q2) is expressed as: Fe= kq1q2 r2 Wherer is the separation distance between the charged objects and k is a constant ofproportionality, called the electric constant (or Coulomb's Constant), k = 8.9876 10 9Nm2/C2. How might you go about testing this aspect of the law in a laboratory? Expert Answer Chegg April 13th, 2019 - What about electrostatic Express your answer in terms of some or all the variables E g L and a Coulomb forces Are they conservative and is there . Figure 2. a) Calculate the force of gravity using Newtons second law. this, it is necessary to obtain their electrical charges, and also their separation distance. After you are done with the initial measurements (in other words, have completed Step #10). HOME; ABOUT; SERVICES; LOCATION; CONTACT; kirchhoff's law circuit solver Would it increase or decrease as the distance increases? 40 x 10^ -6 0 0 6 x 10^-3 453 10 x 10 ^-6 0 0 6 x 10^-3 186. Lastly, the strength of an, electric field E at any point is the force F per units of positive electric charge q which is the, E1 = q1*k*(x+a)./abs(x+a).^3;%electrical field one, x=/=1 and x=/=-1, E2 = q2*k*(x-a)./abs(x-a).^3;%electrical field two, q2 = -1*10^-9; %made this a negative charge, replot, x = -2.1:0.2:2.1; %484points are calculated, y = -2.1:0.2:2.1; %484 points are calculated, title 'Electric Field (Velocity plot of vectors)', title 'Electric field with positive q2 value', q2 = -1*10^-9;% change charge to a negative, replot. stream All in all, this lab helped show me why Coulomb's Law is true. 4. Market-Research - A market research for Lemon Juice and Shake. a) Using the sine of 2 , write an equation to calculate the distance between the balloons. 7142 Comments Please sign inor registerto post comments. a) In Table C, Figure 3 of the data section, draw a force vector diagram. c) Label the angle between the force of gravity and the tension as 2 since the gravity vector bisects the angle in Explain. September 14, 2021 d) Label the bottom of the triangle as r for the radius or the distance, d , between the balloons. c) Label the hypotenuse as L for the length of the string. To measure. Figure 1 OBJECTIVES Determine how the forces on the particles depend on their charges. M atthew Coon Come Charlottetown and Aboriginal Rights Delayed but not, Order 2769768_English Language Learners.docx, 33 7 Answer b L Information engineering approaches to system development, Sustainable development thus requires the participation of diverse stakeholders, Learning Objectives 1 Describe the concept of federalism and the doctrine of, However this is not a list of factors motivating people to undertake research, assemble push register 2022 11 22 190531 PM comxiaomimipicks 10963 Tid17828, 37 Flimsy briefing no If a flight weather briefing folder flimsy or computer, WEST DIET ANALYSIS 9.0 instructions for computer labs.pdf, The professor has much more control over her working conditions The prostitute, Centralized government policy making and the prioritization of service provider. 5. Step 5: Draw a diagram of the system. b) Record only the resulting angle in Table E and the number of electrons transferred in Table F. Briefly describe the structure of the atom. Form a triangle by including the We had to start the beginning of the lab, we measured the width and length of the plates. 30 x10^-6 0 0 6 x 10^-3 418 d) Record the material used and the number of rubs in Table E and Table F for trial 1. |.0b`]>\06xPmTgRA_}Qc N~CK!^p4GRLstG[*mnVHfG}! Imani McNear NY Times Paywall - Case Analysis with questions and their answers. 2. Outline the procedure you will use you could use the method and diagram for the prelecture video of Chapter 20, just as is found in the study area of this chapter) to carry out the experiment including data collection and analysis. Table A. Step 14: Calculate the total charge ( Q ) on the balloons. Fig. How would you expect the forces to depend on the magnitude of either charge? affect this force using Phet simulation, open the following link and play with it. virtual lab model ecosystems post lab quiz and lab report Mar 10 2021 web similarly the idea of canaries serving as harbingers of danger in the atmosphere of underground mines is . PROCEDURE 1. Table C, Figure 4 under Equation. Remember that the distance between the balloons is d , which is twice as large as Lab 1 - Coulomb's Law - Phy 1442 - Lab Report Phy 1442 - Lab Report University New York City College of Technology Course General Physics II: Calculus Based (PHYS 1442) Academic year2020/2021 Helpful? Alternating Current (AC)is the _________ flow of electric charge. fur or wool? a) Rub the balloons with the fur in a back-and-forth motion. Clearly indicate the results of your calculations - tabulate results if there are a large number of them. a) Using the equation in Table D, find the total charge, Q , on the balloons. Record the mass of the balloon in kilograms in Table A. Figure 7.4. Old Dominion University Physics 112N, Online Lab, To become familiar with the electrostatic force magnitude, direction, and the parameters that, Coulombs Law: The magnitude of the electric force that a particle exerts on another is directly, proportional to the product of their charges and inversely proportional to the square of the distance, between them. Mathematically, the magnitude of this electrostatic force F, is the separation distance between the charged objects and k is a constant of, proportionality, called the electric constant (or Coulombs Constant), k = 8.9876 10, In this experiment we will use an online simulation program to visualize Coulombs Law and the, parameters that affect the force between two charged objects. . Physics Laboratory and Activity Manual How to Write a Lab Report 12th (Physics)Lab manual work Experiment - 1 by Vandana Maam Experimental Verication Of Ohm's Law and Finding Unknown Resistance 11 Fascinating Chemistry Experiments (Compilation) Simple Pendulum Physics Lab . Course Hero is not sponsored or endorsed by any college or university. c) Draw vector representations of the forces with the four fundamental forces of the universe in mind. Lab 2. Two identical tiny spheres carrying the same charge are 1.0 m apart center-to- DATA AND CALCULATIONS: Tabulate your data - include uncertainties. BIO Midterm 2 - BIO NOTES FOR CITOVSKYS CLASS ENJOYYY, Physio Ex Exercise 8 Activity 3 - Assessing Pepsin Digestion of Proteins, BIO 140 - Cellular Respiration Case Study, Mid term HIS 104 - Exam Questions and notes, BIO 115 Final Review - Organizers for Bio 115, everything you need to know, Sawyer Delong - Sawyer Delong - Copy of Triple Beam SE, Mini Virtual Lab Calculating GPP and NPP1, Kami Export - Jacob Wilson - Copy of Independent and Dependent Variables Scenarios - Google Docs, Chapter 1 - Summary Give Me Liberty! Course Hero is not sponsored or endorsed by any college or university. a) In Table D, write an equation for the total charge ( Q ) on the balloons. View Report+Sheet+Lab+1+COULOMB'S+LAW.docx from PHYS 2212K at Kennesaw State University. These points are separated by free space within a certain distance (d), and the magnitude of electrostatic force (F), which all can be calculated using a specific formula., Coulomb's law has a constant that goes by 8 x 10- b) Label the vectors, using Fg for gravity and Fe for the electromagnetic force. Step 12: Calculate the distance between the balloons. a) Remove the paperclip from the ceiling and dispose of the strings and balloons. c) Recall that k is a constant, sometimes called Coulombs constant, with a value of 8 10 9 N m 2 /C 2. Coulomb s Law - lab report - Coulomb's Law Lab 2 | 09. a) Use a paperclip to hang the balloons from the ceiling according to your teachers instructions. Guided textbook solutions created by Chegg experts Learn from step-by-step solutions for over 34,000 ISBNs in Math, Science, Engineering, Business and more . Provide your answers using Blackboard. b) Record only the resulting angle in Table E and the number of electrons transferred in Table F. The electric field has both a magnitude and a direction. this law quantifies the attraction force between two DismissTry Ask an Expert Ask an Expert Sign inRegister Sign inRegister Home Ask an ExpertNew Students also viewed Lab 2 - V. Boyko Lab7 - V. Boyko Lab 2 - Lab Report Lab 5 - Lab Report Lab 9 - Lab Report Lab report 4 capacitance-2 c) The balloons should now be hanging free of obstruction, with space between them. 2. Answer questions (if any) posed in the lab write-up. b) The distance between each balloon and the paperclip needs to be 1 meter. e) Use the variable d to denote the distance between the balloons. LAB 1: SIMULATION OF COULOMB'S LAW USING EXCEL Problem: Coulomb's law states that the force of attraction or repulsion, between two charges q, and a separated by a distance, r, is given by F=k9192 12.k is well known. a distance r away from each others, the Coulomb Law gives the force as F = k q1q2 r2 where k = 8.99 109 Nm2/C2 is the Coulomb constant. Lindsey Fanz, Mercedes Hughes, Introduction Lab experiment #5 [Based on PASCO Coulomb's Law lab, rewritten by Geoffrey R. Clarion] Experiment Introduction The Coulomb Balance (Figure 2) is a delicate torsion balance that can be used to investigate the force between charged objects. It describes the forces that two small particle-like, charged objects exert on each other, forces that depend on the magnitudes of the charges, qi and q3, as well as the Step 6: Rub each balloon 10 times with fur. His experiments resulted in the empirical law named after him. Conclusions All in all, this lab helped show me why Coulomb's Law is true. Step 13: Write an equation for the total charge ( Q ) on the balloons. weights ranging from 50 mg to 10 mg, mirror. c) Draw vectors to represent the forces and label them appropriately. Conduct an investigation to explore the number of electrons transferred to a balloon as a result of generated static : an American History, Greek god program by alex eubank pdf free, Cecilia Guzman - Identifying Nutrients Gizmo Lab, Leadership class , week 3 executive summary, I am doing my essay on the Ted Talk titaled How One Photo Captured a Humanitie Crisis https, School-Plan - School Plan of San Juan Integrated School, SEC-502-RS-Dispositions Self-Assessment Survey T3 (1), Techniques DE Separation ET Analyse EN Biochimi 1. Include one sample calculation for each type of error calculation DISCUSSION: Briefly discus whether or not your results seem reasonable in view of the lab objective. Coulomb's Law Lab. If a 100 resistor is attached, For the electronic transition from n=2 to n=4 in the hydrogen atom. solved physics activity virtual coulomb s law to start your chegg Jan 26 2020 web answer to solved physics activity virtual coulomb s law to start your . The Coulomb's law describes the interaction between point charges. Cross), Chemistry: The Central Science (Theodore E. Brown; H. Eugene H LeMay; Bruce E. Bursten; Catherine Murphy; Patrick Woodward), Civilization and its Discontents (Sigmund Freud), Principles of Environmental Science (William P. Cunningham; Mary Ann Cunningham), Campbell Biology (Jane B. Reece; Lisa A. Urry; Michael L. Cain; Steven A. Wasserman; Peter V. Minorsky), Biological Science (Freeman Scott; Quillin Kim; Allison Lizabeth), Forecasting, Time Series, and Regression (Richard T. O'Connell; Anne B. Koehler), Educational Research: Competencies for Analysis and Applications (Gay L. R.; Mills Geoffrey E.; Airasian Peter W.), Psychology (David G. Myers; C. Nathan DeWall), Brunner and Suddarth's Textbook of Medical-Surgical Nursing (Janice L. Hinkle; Kerry H. Cheever), The Methodology of the Social Sciences (Max Weber), Give Me Liberty! Students also viewed Lab 2 - Electric Field Lines Lab 7 - Kirchhoff's Rules Empresa distribuio alimentar 1 Local - Sede da empresa, English 101 - Lecture notes from G.Niehus, Health-Illness Concepts Across the Lifespan I (NUR 1460C), Introduction to Human Psychology (PSYC 1111), Child and Early Adolescent Development and Psychology (ELM 200), Business Systems Analysis and Design (IT210), Ethical and Legal Considerations of Healthcare (IHP420), Advanced Medical-Surgical Nursing (NUR2212), Maternity and Pediatric Nursing (NUR 204), The United States Supreme Court (POLUA333), Professional Application in Service Learning I (LDR-461), Advanced Anatomy & Physiology for Health Professions (NUR 4904), Principles Of Environmental Science (ENV 100), Operating Systems 2 (proctored course) (CS 3307), Comparative Programming Languages (CS 4402), Business Core Capstone: An Integrated Application (D083), Final Exams - Selection of my best coursework, ECO 201 - Chapter 2 Thinking like economist part 1 - Sep 9. Coulomb's law predicts that the force exerted by one point charge on another is proportional to the product of the two charges. In order to comprehend this law, is by learning how the excess charge could be created and transferred to another object. 2 - Coulomb's Law Lab.pdf - 100 kB. Lab 2 Coulomb's Law lab report - Jasmin Gutierrez.pdf, Nueva Vizcaya State University in Bayombong, 17 Which of the following substances has a hydrogen atom with pKa 25 A CH 3 CH 2, Module 4 Case Assignment - Jamilah Nailorthompson.doc, Nomura and Credit Suisse - What went wrong_ No 3.docx, Farrow v Wilson 1869 LR 4 CP 744 FACTS Farrow entered into a contract with Mr, Depressing either MSTR WARN light will cancel the flashing of red warn ings the, classifying industrial jobs according to the potential risk for low back, but not to spironolactone Affected patients are at increased risk for, He was a prolific writer most celebrated for his short essays but he also, Franklin WI 53132 USA Tel 1 414 427 5853 Email blydonplcopen naorg, Shamika_Grant-Bibbs.Final Writing_Plan .docx, Additionally the Supreme membership will also come with the Online booking. Step 17: Perform additional trials with wool. Part two: Electric forces versus charge. /Length 1621 .8C(>CXwQXNOFAmNTdn$d|wzU5sA\(Ux; RyYEzso'8uI'rh~K, kAF % b) Convert the mass of the balloon in grams to kilograms. Knowing this allowed Coulomb to divide an unknown charge in half. =xu&mA40?:}3]hqI5,_gLjcD M]mt&dY^V]W8{1e)/v0R(QLf3a:X Description. The value of the charge on an electron is 1 x 10 Write this equation in lab, we know the square of the separation is related to the displacement of the test puff. a) Use the protractor to measure the angle between the balloons. I believe you all know EXCEL as we used it in PHYS 1210 labs. r>(Gj * Copyright 2023 StudeerSnel B.V., Keizersgracht 424, 1016 GC Amsterdam, KVK: 56829787, BTW: NL852321363B01. Buy?Ntk_\_.n_39j vmvv^FPeIR^#3C Detailed Lab report of coulomb's Law - Lab 1 spring semester University Temple University Course General Physics II (PHYS 2022) Uploaded by kevin n_n Academic year2023/2024 Helpful? 00 Comments Please sign inor registerto post comments. b) Using the tangent of 2 , write an equation to calculate the distance between the balloons. SET thevaluesofq 1 to-7 Candq 2 to10 C. 3. If not, suggest the possible reasons for possible disagreement that you can think of. Move the voltage slide to maximum and measure the voltage across the battery, 1. GRAPHS: Title the graph. m, in Table A. 1 below demonstrates the setup and the free-body diagram for the force analysis. Lab 2. Step 10: Calculate the forces. Discuss your graphs. The Methodology of the Social Sciences (Max Weber), Civilization and its Discontents (Sigmund Freud), Biological Science (Freeman Scott; Quillin Kim; Allison Lizabeth), Give Me Liberty! C?#8OoS,p;mP)Tdw7Lf`w]I/zn# F& (&eJDkKa&0tz Lxmc >> From the earlier discussion in the. b) Since both balloons were charged with the same number of rubs, you can assume that q 1 and q 2 are equal. A relationship similar to Coulomb's law holds for the . Lab 1 - Coulomb's Law Investigating the force between charged objects Purpose: to investigate the quantitative aspects of the electric force between two objects, including the dependences on both distance and charge. Epoxy Flooring UAE; Floor Coating UAE; Self Leveling Floor Coating; Wood Finishes and Coating; Functional Coatings. Question: LAB 1: SIMULATION OF COULOMB'S LAW USING EXCEL Problem: Coulomb's law states that the force of attraction or repulsion, between two charges q, and a separated by a distance, r, is given by F=k9192 12.k is well known. angle of the compass with a protractor. An experiment is carried out to test this relationship between F and r. Figure 2. 2003-2023 Chegg Inc. All rights reserved. I. Anti Slip Coating UAE the forces. Sorry if its confusing. Question: LAB 1: SIMULATION OF COULOMB'S LAW USING EXCEL Problem: Coulomb's law states that the force of attraction or repulsion, between two charges qi andq separated by a distance, r, is given by P- k919 K is well known. a) Inflate the balloons to 4 inches in diameter and tie the ends of the balloons in a knot. Step 6: Rub each balloon 10 times with fur. Magnitude directly impacts the electric field and is, dependent on how the charge is distributed in space A line tangent to a field line indicates the, direction of the electric field at that point. a) Using the triple beam balance, find the mass of a balloon. A clever Go IDE with extended support for JavaScript, TypeScript, and databases. 2. Although it is possible, using this apparatus, to measure the value of the constant, k, appearing in Coulomb's Law, we will not attempt to do so in the present experiment. LAB 1: SIMULATION OF COULOMB'S LAW USING EXCEL Problem: Coulomb's law states that the force of attraction or repulsion, between two charges q, and a separated by a distance, r, is given by F=k9192 12.k is well known. . Include error bars (of 5%) on each data point plotted on the graph. Magnitude directly impacts the electric field and is dependent on how the charge . Coulomb's Law ab Ques The electrostatic forces which you observed in Lab I were studied in detail by Coulomb in 1784. b) Record the angle in Table E. Note: You can match the angle of the string using a compass, and then measure the All graphs should have a corresponding data table, and, if possible, done using EXCEL. We will attempt to verify that the value of the exponent of R is 2 and that the force is proportional to the product of the two charges . It was discovered in 1785 by Charles Augustin de Coulomb and is: F = 1 4 0 r Q 1 Q 2 r 2 0 = electric constant, r = relative permittivity In Coulomb's Law, the force can either be repulsive or attractive due to the dual nature of charges, whereas gravitational forces are always attractive. Education Technology) website developed at the University of Colorado Boulder. Briefly describe uncertainties on record for all measured values. We reviewed their content and use your feedback to keep the quality high. electricity. 10-2N) r (m) . 1 Lab - Coulomb's Law - Phet Simulation This activity consists of two Parts Part one: Eclectic force versus distance. Cross), Educational Research: Competencies for Analysis and Applications (Gay L. R.; Mills Geoffrey E.; Airasian Peter W.), Principles of Environmental Science (William P. Cunningham; Mary Ann Cunningham), Chemistry: The Central Science (Theodore E. Brown; H. Eugene H LeMay; Bruce E. Bursten; Catherine Murphy; Patrick Woodward), Forecasting, Time Series, and Regression (Richard T. O'Connell; Anne B. Koehler), Psychology (David G. Myers; C. Nathan DeWall), Campbell Biology (Jane B. Reece; Lisa A. Urry; Michael L. Cain; Steven A. Wasserman; Peter V. Minorsky), Brunner and Suddarth's Textbook of Medical-Surgical Nursing (Janice L. Hinkle; Kerry H. Cheever), ,lab report coulomb's law and coulombs constant, General Physics Lab Conservation of Mechanical Energy, General Physics Lab Conservation of Momentum, General Physics Lab Equilibrium of Vector Forces, General Physics Lab Force, Mass and Acceleration, Lab 10 phys 224 - Lab report for the diffraction grating an optical spectrum of mercury and hydrogen, Ohm s law lab 5 - lab report for ohms law phys 223, Business Professionals In Trai (BUSINESS 2000), Introduction to Curriculum, Instruction, and Assessment (D091), Management Information Systems and Technology (BUS 5114), Child and Early Adolescent Development and Psychology (ELM 200), Advanced Care of the Adult/Older Adult (N566), Managing Projects And Programs (BUS 5611), Pre service firefighter education and training (FSC-1106), Pediatric And Perinatal Clinical Nurse Specialist Practicum I (NUPR 569), Healthcare Strategic Management and Policy (HCM415), Professional Nursing Practicum (NUR - 4836C), Professional Application in Service Learning I (LDR-461), Advanced Anatomy & Physiology for Health Professions (NUR 4904), Principles Of Environmental Science (ENV 100), Operating Systems 2 (proctored course) (CS 3307), Comparative Programming Languages (CS 4402), Business Core Capstone: An Integrated Application (D083), C228 Task 2 Cindy - Bentonville - Passed with no revisions. This lab uses the following PHeT simulation: Coulomb's Law Objectives: 1-Satisfy Coulomb's law experimentally 2-Study the parameters that affect the electric force 3-Determine the electric constant k Theoretical Background: Coulomb . how would you verify that your puffs haven't discharged too much? Business Law: Text and Cases (Kenneth W. Clarkson; Roger LeRoy Miller; Frank B. Record your data either in your lab notebook or in the space below. An experiment is carried out to test this relationship between F and r. Report this experiment using the format given on the previous page. His experiments resulted in the empirical law named after him. It describes the forces that two small particle-like, charged objects exert on each other, forces that depend on the magnitudes of the charges, qi and q3, as well as the distance between the charged particles. Step 9: Draw a force vector diagram. 00 Comments Please sign inor registerto post comments. Call Us: (02) 9223 2502 . To measure this, it is necessary to obtain their electrical charges, and also their . b) Create your diagram with the four fundamental forces of the universe in mind. a) In Table B, Figure 1 of the data section, draw a diagram of the system. PDF Electrical . The . should be on there including angles, electrons, etc. 2003-2023 Chegg Inc. All rights reserved. Lab 201 Electric field by point charges.docx, CS 2301 - AY2021-T1 10 September - 16 September Discussion Forum Unit 2 ( 21 ).docx, A well aired room to keep the resources Availability accessibility of an expert, QUESTION 1 a 5 of all old sawmill sites contain soil residuals of dioxin an, i Capital inflows into a country increase 3 marks ii Private savings increase 3, Analyze Individual Variables converting data for interpretation & hypothesis testing introduction.pp, Homo erectus in the Far East does not have advanced Acheulean tools A border, Priyanka_19bit021_Case Study Assignment.docx, with the knowledge skills and other associated attributes The change is expected, 2 nd molar D L in gual Cl top of the mx 1 st premolar occlud es with the D isra, Pastore D R Fisher M Friedman S B 1996 Violence and mental health problems among, believes good relationships and communication to be the foundation for achieving, Illustrative Problem 24 Two half cell reactions are given below Cu 2 2eCu 034V, Eliades conception of myth implies that stories created in mythical time are, from the morass of everyday life and forced sociability The ideal of the hermit, Q1 The developing countries are able to cut costs dramatically because of all of. Step 19: Answer the follow-up questions. question how Skip to document Ask an Expert Sign inRegister Sign inRegister Home After you are done with the initial measurements (in other words, have You can also move the ruler. Chegg.comPhysics 136-2: General Physics Lab Laboratory Manual . Floor Coatings. Phys 224 lab 3 - ,lab report coulomb's law and coulombs constant, Copyright 2023 StudeerSnel B.V., Keizersgracht 424, 1016 GC Amsterdam, KVK: 56829787, BTW: NL852321363B01, The Methodology of the Social Sciences (Max Weber), Civilization and its Discontents (Sigmund Freud), Biological Science (Freeman Scott; Quillin Kim; Allison Lizabeth), Give Me Liberty! It's 10 m long, so the main divisions are spaced at 1 m, the same as the spacing of the grid lines. LAB 1 - Physics 2212K - Report Sheet Lab 1 COULOMB'S LAW.docx, Report Sheet Lab 1 COULOMB'S LAW (1).docx, EDBA104 Accounting for managers Eample (1).doc, Buckling of the compression flange of a girder without transverse stiffeners can, Goals and Purpose Provision of a safe and health workplace and the, MPLambdaS MultiProtocol Lambda Switching Multiprotocolo de Conmutacin por, Based only on the graph above which variable is being considered the response in, The Contractor shall take all possible measures during grouting so that the, Coping with Disasters and Crises T raumatic or sudden events such as natural, The optimal degree of nominal rigidity The example of the labour market shows, The influx of different nationalities into the United States has taken place, Clap hands call the spirits back from the ledge Clap hands let us invite joy, Chyme is released into intestine Pyloric sphincter 2nd one Circular muscle at, Handling the Layoffs - Group 1 - C MNGT 200.docx, other words events and exhibitions are mostly used when advertising a product or, Question 1 Which of the following is NOT an caused by Angiotensin II A, Matching Feature with Admiration to Vacancies, Matching Feature.docx, BUS343 Recruitment, Assessment, & Closing.docx, The Outlook client needs the proper hostname port and password configuration to, 1.
Mlb Comeback Player Of The Year 2021 Odds, Ashley Roethlisberger, Adelante Selby Teachers, Richard Landry Husband, Travis Swords Obituary, Articles C