Midterm—Physics II Lab, Spring 2012 50 pts Name___________________________ Equations: V IR R L A Req , parallel 1 R1 1 R2 1 R13 ... Rx R Rb Ra Req ,series R1 R2 R3 ... Multiple Choice (1 pt each) ____ 1. If the resistance in a circuit is constant and the current is increased, how will the voltage be affected? a. Decreases c. Increases b. Does not change ____ 2. If 3 resistors are connected in parallel, what is equal across each resistor? a. Current c. Resistance b. Potential (Voltage) d. None of the Above ____ 3. If you increase the diameter of a wire, what happens to the resistance? a. Increases c. Remains the same b. Decreases d. Depends on the resistivity ____ 4. Equipotential lines are always ___________ to electric field lines. a. Parallel c. at 45 degree angles b. Perpendicular d. Tangent ____ 5. What is the purpose of a wheatstone bridge? a. to measure an unknown resistance b. to measure an unknown voltage c. d. to measure an unknown current to confound its user Short Answer 1. (4 pts) Draw 6 electric field and 6 equipotential lines for this configuration of charges. Let the lines span across the entire page. 2. (9 pts) Given this data for a particular circuit consisting of a resistor in series with a power supply, determine (graphically) the voltage provided by the power supply. Use the attached graph paper. R ( ohms) 1 2.4 3.2 5.4 8 11 I (amps) 3.3 1.6 1.2 0.5 0.4 0.2 V=______________ 3. (3 pts) Consider this circuit. What is the potential of the battery? V=__________________ 4. (5 pts) Three resistors of 2, 10, and 8 Ω are in series with a power supply providing 40 V. What is the current and potential in each of the resistors? 5. (7 pts) Consider the following circuit. What is the equivalent resistance? What is the potential across each resistor? What is the current through each resistor? Req=_____________ V1= _____________ V2= _____________ V3= _____________ I1= _____________ I2= _____________ I3= _____________ 6. (4 pts) What components or parts make up an ammeter? 7. (3 pts) How do you hook up an ammeter in a circuit? 8. (3 pts) How can you increase the range of a voltmeter? 9. (7 pts) This figure shows a Wheatstone Bridge. Derive the equation for the unknown resistance R x. Show all steps.