Series and Parallel Lab

Series and Parallel Lab

Electrical safety

• Always have the power supply turned off when you are connecting and disconnecting wires.
• Never touch an exposed wire or exposed metal while the power is on.
• If you are unsure about your setup, ask me to check it.

Measuring the voltage difference between two points.

• The wires should be connected to COM and V.
• Set the dial to the green 20 V or 2 V setting.
• Touch the two wires to the two points where you are trying to measure the voltage.
• Turn the meter off when you are finished using it.

Measuring the current through a point.

• The wires should be connected to COM and mA.
• Set the dial initially to the green 200m setting.
• Find the point at which you are trying to measure the current AND DISCONNECT THE CIRCUIT AT THIS POINT.
• Touch the two wires from the ammeter to the wires that you just disconnected in your circuit.
• NEVER TRY TO MEASURE CURRENT WITHOUT BREAKING YOUR CIRCUIT FIRST.
• You may change the setting to 20m, 2m, or 200 as necessary. Pick the setting that gives you the most decimal points in the reading.
• If the dial is set to 200m, 20m, or 2m, then the number on the meter is in milliamps (10-3 amps). If the dial is set to 200, then the number on the meter is in microamps (10-6 amps).
• Turn the meter off when you are finished using it.

Procedure

• For each part of this lab (series and parallel), you will be measuring two circuits: one with identical resistors and one with different resistors. There is a total of four circuits for this lab.
• For each of your circuits, be sure to record the color codes for your resistors.
• Set the voltage knob on the power supply to approximately 10 V. You will not be changing this during the lab.
• Copy the tables below onto your own page. You’ll have two tables for resistors in series and two tables for resistors in parallel.

Series Circuit

Parallel Circuit

Questions

• What can you conclude about the current flowing through each of two resistors in series?
• What can you conclude about the voltage across each of two resistors in parallel?
• What can you conclude about the voltage across each resistor in series compared with the voltage across the combination of resistors?
• What can you conclude about the current flowing through each resistor in parallel compared with the current flowing through the combination of resistors?
• Pretend that the two resistors wired in series were really just one resistor. Use the current through this pretend resistor and the voltage across it (A-C) to calculate the total resistance. Compare this resistance to the actual resistances of the two resistors. What can you conclude about the resistance of two resistors in series?
• Pretend that the two resistors wired in parallel were really just one resistor. Use the current through this pretend resistor (at point A or point F) and the voltage across it to calculate the total resistance. Compare this resistance to the actual resistances of the two resistors. What can you conclude about the resistance of two resistors in parallel?