1418-1, Capacitors

and Capacitive

Circuits

Experiment 6: Using Capacitors in

Voltage-Divider Networks

Objective

• To verify that capacitors can be used

in AC voltage-divider circuits without

the use of resistors.

Introduction

• Capacitors can be used in an a-c voltage

divider application in a circuit in a

manner similar to a resistive voltage-

divider network.

Note: Care must be taken when

capacitors are used in this way, since their

capacitive reactance is frequency-

sensitive and the design will be good only

within a narrow range of frequencies.

Basic two component ckt

• Where frequency enters into a voltage-

divider design, resistors and not

capacitors should be used.

• Remember, when capacitors are used in

voltage-divider circuits, they usually

require a constant frequency signal

source.

• Capacitors consume little power, so the

power drain will be small in a capacitive

voltage-divider network.

Basic theory review

• A voltage-divider circuit is a typical

series circuit containing two or more

components. To simplify the experiment,

we will be using only two capacitors.

• The following slide will review the

general rules for a series circuit and we

will review some of the formulas needed

to analyze the circuit.

1. The current is the same through all

parts/components of the circuit.

a) The current “I” equals the applied

voltage “E” divided by the total circuit

impedance “Z”.

2. The applied voltage must be equal to the

sum of all the voltage drops.

IT for Reactive Circuit

Formulas for E1 & E2 for

reactive circuits

Formula for E1 for Capacitive

Circuit

Procedure

1. Calculate the voltages for the circuits

a) Record values in table in lesson

2. Build the following three circuits.

3. Measure the voltages you calculated

4. Calculate %error using formula given

for each circuit and record %error

Circuit 1

Ckt 1 wiring example:

%error formula

Circuit 2

Ckt 2 wiring example:

%error formula

Circuit 3

Ckt 3 wiring example:

%error formula

Final Discussion

• The data from the three voltage-divider

circuits verified the voltage-divider

principle when capacitors are used as the

only components in the circuit.

• In each case, the division of voltage was

predictable (with the values of the

capacitors known).

• Remember to use the discussed formulas

when predicting the values of EC1 & EC2

and any other values in a multicomponent

divider circuit.

Questions?

Resources

• Rubenstein. (2001). Lesson 1418:

Capacitors and capacitive circuits.

Cleveland: Cleveland Institute of

Electronics.

The End

Developed and Produced by the Instructors in the CIE Instruction

Department.

© Copyright 04/2012

All Rights Reserved / April 2012