Lab #30
Series and Parallel Circuits
Introduction:
An electrical circuit is a continuous path or array of paths through which an
electrical current can flow.
The two different ways in which components of a
circuit can be connected are called "series" and "parallel".
In a series
connection, components are connected one after another; therefore, the same
current flows through all of them.
In a parallel connection, the circuit components
are
connected side by side. That is, the positive and negative sides of each
component are respectively connected together; therefore, each has the same
potential drop across. In this lab, we will explore measurements of current and
potential difference in simple circuits. Also, we will attempt to verify the textbook
expressions for
the equivalent resistance of components connected in series and
in parallel, and for the power dissipation in a resistive load.
For instance, for a
circuit consisting of any three resistance values R
1
, R
2
, R
3,
the equivalent
resistance in series R
s
and in parallel R
p
are,
R
S
= R
1
+ R
2
+ R
3
+ … + R
N
(1)
and
1/ R
P
= 1/ R
1
+ 1/ R
2
+ 1/ R
3
+ … + 1/ R
N
,
(2)
respectively.
Apparatus:
A connection board ("breadboard", see figures 1 & 2) with 3 resistor sockets, a
multimeter with ammeter and voltmeter, and a variable voltage supply set for 10
Volts output.
Procedure:
When you are building a circuit, be sure the power supply is turned off the whole
time, until you are ready to take measurements. Use only the plug-in connecting
wires supplied. If you need more wires, ask your instructor.
When connecting the digital multi-meters (DMM), start out by setting the
instruments to their least sensitive scale. You may switch to a more sensitive
(smaller value) scale to get a more precise reading. For example, suppose you
have found a voltage to be around 5 Volts after measuring it with the DMM set on
a 200 Volt scale. To get a more precise reading, do not switch to a 2 Volt scale