Name: ________________
Electric Circuits - PARALLEL CIRCUITS (lab)
Purpose: to investigate the properties of simple MULTI-LOAD circuits in which loads are wired
IN PARALLEL.
Part 1: Simple 1-Load Circuit Circuit
Use a single light-bulb unit to build the simple circuit shown in the schematic below (Figure #1).
a) Measure the current in the circuit by inserting the multimeter in line
(between the light and the source) as shown in the schematic (Figure #2).
b) How much current flows through the circuit? ______
c) Measure the voltage across the bulb. V = ______
d) Use Ohm’s Law to determine the resistance of the single light. R = ______
Fig. 2
Fig. 1
A
Part 2: Parallel Circuits
A) Use TWO (2) light-bulb units to build the simple circuit shown in the schematic below
(Figure #7). Notice that this second light bulb has been placed IN PARALLEL with
the first.
a) Insert the multi-meter in line as shown in the schematic (Figure #4).
b) How much current flows through the circuit? ______
c) How does this compare to the single bulb circuit’s current? _______
d) What happened to the brightness of the bulbs (dim or remain bright)? __________
e) Measure the voltage across each bulb. V = ______, V = ______
f) Use Ohm’s Law to determine the resistance of the two lights together. R = ______
Fig. 3
Fig. 4
A
B) Now, use THREE (3) light-bulb units to build the simple circuit shown in the schematic below
(Figure #9). Notice that all three bulbs are IN PARALLEL with each other.
a) Insert the multi-meter in line as shown in the schematic (Figure #6).
b) How much current flows through the circuit?
______
c) How does this compare to the previous current(s)? _______
d) What happened to the brightness of the bulbs? ______
e) Measure the voltage across each bulb. V = ______, V = ______, V = ______
f) Use Ohm’s Law to determine the resistance of the three lights together. R = ______
Fig. 5
Fig. 6
A
C) Unscrew one of the bulbs. What happens to the other 2? ___________________________
Explain why. ______________________________________________________________
______________________________________________________________
D) In the space below, make a general statement about the effect on current in a circuit when loads are
added IN PARALLEL. “When loads are added to a circuit in parallel, ….”.
E) In the space below, make a general statement about the effect on total resistance in a circuit when loads
are added IN PARALLEL. “When loads are added to a circuit in parallel, ….”.