ENSC 220
ELECTRIC CIRCUITS I

Lab #1: KVL and KCL

OBJECTIVE:
Using the circuit below, you can verify KVL by showing that the sum of voltages around the loop Vin -> R1 -> R2 is zero. You can also verify KCL by showing that the currents entering node "a" sum to zero.

PREPARATION:

  • Read Lab Handbook 2.2.2 (Lab Power Supplies) and 2.2.3 (DMM).
  • Read Lab Handbook 2.3.3 (Resistors) and 2.4.1 (Breadboards).
  • Derive equations for all circuit voltages and currents in terms of Vin, R1, R2, and R3.

    EQUIPMENT:

  • Basic lab tools and breadboard
  • Digital multimeter (DMM), Fluke 8010A
  • DC power supply

    NOTES:

  • When making circuit changes, turn down the current on the power supply and turn off the power supply. Turn it on again only after checking the circuit carefully.
  • Check the multimeter setup before hooking it into the circuit. Improper setup can give incorrect readings and/or damage the meter.
  • IMPORTANT: When building the circuit, select resistor values such that the power generated in each resistor in the circuit will be well below its 1/4 watt power dissipation rating.

    METHOD:

    1. Choose appropriate R1, R2, and R3, and measure their values using the DMM.

    2. Construct the circuit and adjust Vin=1.0 V (approximately), under load.

    3. KVL: Calculate the expected voltages across R1 and R2, and then measure them.

    4. KCL: Calculate the expected currents through R1, R2, and R3, and then measure them.

    DISCUSSION:

  • Find the DMM accuracy for measuring DC voltage, current, and resistance.
  • Choose one example from your calculations and show how equipment accuracy and measurement errors propagate through equations to affect expected values.
  • Explain how the measurement process itself affects the resistances, voltages and currents that you are measuring.
  • Reconcile each measurement against the expected value. You should be able to explain any differences within a specified range of certainty.
  • Can you think of a more effective method of confirming KCL?
    Last modified: Wed Aug 12 21:31:14 PDT 1998.