# Parallel Circuit Lab by malj

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Series Circuit Lab
Purpose: to observe the effects on current, voltage and resistance when electrical devices are connected in a Series
circuit.

Procedure Part I:
Construct a simple circuit which contains only a power supply and a light bulb. Add an ammeter and voltmeter in
the appropriate places to measure the current and voltage that the bulb experiences.
Set the power supply at five volts. Leave the power supply at this setting for the entire lab.

Data Part I:
Draw the circuit diagram for this circuit. Include all meters. Write the voltage, current and resistance beside the
bulb.

Procedure Part II:
Construct a series circuit which contains 2 bulbs and a power supply. Add an ammeter and a voltmeter in the
appropriate place to measure the current and voltage each bulb experiences.

Data Part II:
Draw the circuit diagram for this circuit. Include all meters. Write the voltage, current and resistance beside each
bulb in the circuit. Record the overall current for the circuit next to the appropriate ammeter.

Procedure Part III:
Construct a Series circuit which contains 3 bulbs and a power supply. Add an ammeter and a voltmeter in the
appropriate place to measure the current and voltage each bulb experiences.

Data Part III:
Draw the circuit diagram for this circuit. Include all meters. Write the voltage, current and resistance beside each
bulb in the circuit. Record the overall current for the circuit next to the appropriate ammeter.

Answer questions 1-5 separately for both parts II and III.
1. What does the sum of the voltages add up to? What should it add up to?

2.   Calculate the percent difference between the overall voltage across the power supply and the sum of the
individual voltages.

3.   How does the current across bulb one compare with the current across bulb two?

4.   Calculate the equivalent resistance of the circuit using the format: Req = R1 + R2 + …

5.   The equivalent resistance can also be calculated by dividing the total voltage by the current. Calculate the value
using this method as well and then compare the two values by using a percent difference.

6.   As a bulb is added in series to the circuit what happens to each bulb’s brightness?

7.   What happens to the total voltage in a series circuit as more devices are added? What happens to the voltage
across each device as more devices are added in series?

8.   What happens to the current going through the circuit as more devices are added?

9.   What happens to the equivalent resistance of the circuit as more devices are added?

Joe Cox
February 1, 1999

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