OHM’S LAW LAB
PURPOSE:
-To verify Ohm’s law for the total circuit and for each individual resistor within a
circuit
-To verify the rules and equations for series and parallel circuits as they relate to
voltage (V) and current (I).
PROCEDURE:
-Diagram each circuit built for circuit A, B, and C.
 Circuit A is a series circuit (required)
 Circuit B is a parallel circuit (required)
 Circuits C is a basic combination circuit (required)
 Circuit D & E are more complex combination circuits (bonus…if time
permits)
-On your diagram, show where the ammeters (A) and voltmeter (V) must be placed to
measure I1, then I2, then I3; and for V1, then V2, and then V3 for each circuit.
-Build the circuits. Measure the following:
R1, R2, R3, V1, V2, V3, I1, I2, I3 AND VT, and IT
* For the bonus circuits, you’ll need 5 values for each variable!
*REMEMBER: Voltmeters and Ohmmeters are always connected in
parallel, Ammeters are connected in series!!!
DATA:
-Construct a table which includes all measured values for V, I and R for circuits A, B, and C.
*Note: Be careful about milliamps, Ketc. WATCH YOUR UNITS!!!
CALCULATIONS:
-Using all of your measured values for your resistors, find the value for Req. Note: This
will be different depending upon what type of circuit this is!!
-Using Req and VTOT, find the theoretical value for ITOT in the circuit. Compare this to
your measured value. Discuss how closely they agree.
-Be sure to use your data to verify Ohm’s Law (V = IR) across each row of your table
(ie: V1 = I1 x R1, etc.). Compare the calculated values to the measured values
-Use your equations from your notes and your data to verify the theory for series and
parallel resistors (ie: in series circuit, VTOT = V1 + V2 + V3… ITOT = I1 = I2 = I3);in a
parallel circuit (VTOT = V1 = V2 = V3… ITOT = I1 + I2 + I3)
DISCUSSION/INTERPRETATIONS:
1. Explain why adding more resistors in parallel decreases the overall equivalent
resistance in a circuit.
2. Explain why the voltage drop in each branch of a parallel circuit is equivalent to the
total voltage of the source.
3. Explain why the current throughout a series circuit is constant.
4. Discuss whether or not this experiment verified Ohm’s Law. Use specific evidence
from your trials to support your answer.