Overview
LAB 4: CHARGES AND FIELDS Part A Theory Please study electric field and potential concept to answer the following questions. 1. Define electric field. Define electric potential difference. Describe each quantity in the equation. 2. Write equations of electric field E and potential V for point charge. Draw electric field line and equipotential surface surrounding single (a) positive charge and (b) negative charge. 3. The electric field line and equipotential line surrounding two charges are shown. The charge q1 = + 2 nC is on left. The q2 = +1 nC is on right. The spacing between two charges is d = 3 m. If r1 is distance from q1 toward q2 along the join line, what is the electric field E and electric potential V at r1 = 1.0 m? k = 8.9876•109 Nm2/C2 Part B Lab Go to PhET website. Click on Simulation/Physics. Under Physics, choose Electricity, Magnets & Circuits. Under Electricity, Magnets & Circuits, Charges and Fields is the 12th simulation (Location might change. A to Z search.). Click to run the Charges and Fields. I. Measure Electric Field E with Charges and Fields Simulation: Basic Operation for Measuring E with Charges and Fields Simulation: Place check marks on Electric Field, Values, and Grid. Drag q1 = +1 nC charge to left side of screen and q2 = ?1 nC to right side of screen (symmetrical distribution about center of screen). Arrange the spacing d = 3 m (6 grids, check with ruler) between q1 and q2. Drag Sensors to measure E, r1 is distance from q1 toward q2 along the join line. Test and understand all functional tools on screen. You must practice figuring out what is the best way to complete the measurement. Data Table 1: Measure Electric Field, Magnitude as E(V/m) and Direction ? or Arrow Drag Sensors to measure E, r1 is distance from q1 toward q2 along the join line. Attach a screenshot of r1 = 0.5 m measurement from the Simulation to lab report. r1 (m) 0.50 1.0 1.5 2.0 2.5 E (V/m) Direction Question: k = 8.9876•109 Nm2/C2 • Show your work of theoretical calculation electric field E at r1 = 0.50 m due to q1 and q2. • Describe the characteristics of Electric Field Lines from your observation. II. Measure Electric Potential V with Charges and Fields Simulation: Basic Operation for Measuring V with Charges and Fields Simulation: Place check marks on Values and Grid (not on Electric Field). Drag q1 = +1 nC charge to left side of screen and q2 = ?1 nC to right side of screen (symmetrical distribution about center of screen). Arrange the spacing d = 3 m (6 grids, check with ruler) between q1 and q2. Drag Voltmeter out of Toolbox (located at right side screen) to measure V. r1 is the distance from q1 toward q2 along the join line. Test and understand all functional tools on screen. You must practice figuring out what is the best way to complete the measurement. Data Table 2: Measure Electric Potential V (V) Drag Voltmeter and place the crosshair at r1 to measure V, r1 is distance from q1 toward q2 along the join line. Place the probe of voltmeter at r1 position. Then, click the Pencil on Voltmeter, an equipotential surface will be shown at r1 position. Repeat this process to complete all measurement. Attach a screenshot of r1 = 2.5 m measurement from the Simulation to lab report. r1 (m) 0.50 1.0 1.5 2.0 2.5 V (V) While keeping all equipotential surfaces on screen, place check mark on Electric Field. Make the screenshot including electric field line and equipotential surface line for submission. Question: k = 8.9876•109 Nm2/C2 • Show your work of theoretical calculation electric potential V at r1 = 2.5 m due to q1 and q2. • Describe the characteristics of equipotential surface and Electric Field Lines from your observation. Part C Discovery Beyond what you have done with Charges and Fields, make few new findings using different charges arrangement, or give real life examples for electric field and potential.