Name: PROPERTIES OF ELECTRIC CIRCUITS Date: Go to www.linville.ca and click on the page Computer Simulations or go to http://phet.colorado.edu/simulations open the Circuit Construction: DC and then click the play button. then select the Lab icon I. Batteries Using the simulation, measure the voltage of the following battery combinations. Record your measurements in the table below. Battery Combo 1 battery Voltage (V) Series Connection Parallel Connection 2 batteries (connected in series) 3 batteries (connected in series) 2 batteries (connected in parallel) 3 batteries (connected in parallel) a. Describe the relationship between the number of batteries and the voltage when batteries are connected in series. b. Describe the relationship between the number of batteries and the voltage when batteries are connected in parallel. c. Give a reason for connecting batteries in series. Identify one technology in which batteries are connected in series. d. Give a reason for connecting batteries in parallel. Identify one technology in which batteries are connected in parallel.
II. Resisters in Series a. Use the simulation to build a series circuit that includes two batteries in series, an ammeter, switch and light bulb. Make a schematic drawing of your circuit in the table. (See the image below to help but note that it has two light bulbs. At this point, use just one!) There are two types of ammeters in the simulation, use the rectangular one on the right. b. Click on the switch to start up your circuit. Is the battery supplying direct current (DC) or alternating current (AC)? Give a reason for your answer. c. Measure the current and the voltage of the circuit. Record the values in the table below. Also note the relative brightness in the table. Note: you must connect the ammeter in series to measure current and the voltmeter in parallel to measure voltage. d. Use Ohm s Law (shown below) to calculate the resistance of the circuit. Record the value in the table. V=IR V=voltage in volts (V) I=current in amps (A) R=resistance in Ohms (Ω) e. Add a second light bulb in series. Measure the current and voltage, then calculate the resistance of the circuit. Record the values in the table. Draw a schematic diagram of the circuit in the table. The image to the right shows how to measure the voltage across two light bulbs f. Add a third light bulb in series. Measure the current and voltage, then calculate the resistance of the circuit. Draw a schematic diagram of the circuit in the table. Number of Light Bulbs (Resistors) in SERIES Schematic Diagram Voltage across battery (V) Current in circuit (A) Resistance of circuit (Ω) Relative Brightness 1 2
3 g. Describe the relationship between the numbers of resisters added in series to the total resistance of the circuit. h. How did the current change as the resistance increased? i. Describe an advantage of a series circuit. j. Measure the voltage across each bulb and then across the batteries. This means one end of the voltmeter is connected to one side of the bulb and the other end of the voltmeter is connected to the other side. Notice how the voltmeter wires are connected to measure the voltage across the 2 nd bulb. Voltage across 1 bulb Voltage across 2 nd bulb Voltage across 3 rd bulb Voltage across batteries What is the relationship between the battery voltage and the total voltage across resistors in a series circuit?
1 2 3 4 k. Click on the other type of ammeter. This type doesn t need to be placed in the circuit. Close the switch and move the crosshairs to the indicated positions. Record your observations. Point 1 A Point 2 A Point 3 A Point 4 A Explain your observations. III. Resistors in Parallel A. Construct a circuit with a switch, 2 batteries, and one light bulb. Measure the voltage and current, and calculate the resistance. Complete the first row of the table below. B. Add a second bulb in parallel. Measure the total voltage and current of the circuit, and calculate the total resistance. Complete the second row of the table below. (The diagram to the right shows you what a parallel circuit looks like.) C. Add a third bulb in parallel. Measure the total voltage and current of the circuit, and calculate the total resistance. Complete the third row of the table below.
Number of Light Bulbs (Resistors) in PARALLEL Schematic Diagram Voltage (V) Current in circuit(a) Resistance of circuit (Ω) Relative Brightness 1 2 3 D. Describe how the current changes as light bulbs are added in parallel. E. Describe how the resistance changes as light bulbs are added in parallel. Provide a possible explanation for this.
F. Modify your circuit to add ammeters as shown. Ammeter 1 Ammeter 2 Ammeter 3 Close the switch and record the current through each ammeter. Ammeter 4: This measures the total current in the circuit Ammeter 1 Ammeter 2 Ammeter 3 Ammeter 4: What is the relationship between the current through parallel resistors and the total current in a parallel circuit? What is the voltage across: Bulb 1 Bulb 2 Bulb 3 Both Batteries Remember that one wire from the voltmeter is on one terminal of the bulb and the other voltmeter wire must be on the other terminal of the same bulb.
G. Make separate side-by-side circuits - one with three bulbs in parallel and one with three bulbs in series. i. By watching the motion of electrons, which one has greater current? Greater Resistance? ii. By observing the relative brightness of the bulbs, which one expends more energy? H. Do you think that your homes circuits are connected in series or parallel? Give a reason for your answer. I. Provide an advantage of using parallel circuits.