Practica Div Vol 1

8/16/2019 Practica Div Vol 1

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Instituto Politécnico Nacional

Escuela Superior de Cómputo

Laboratorio de Análisis Fundamental deCircuitos

Fundamental Analysis of Circuits

Practice No.5

“ Voltage Divider - Part 1: C.D”

Group: 1CV5

Members:

García Barrera Guadalupe

García Macías María del Carmen

García Ortega Oscar Arturo

Teacher: Raúl Santillán Luna

DATE OF COMPLETION: 20th April 2016

DATE OF DELIVERY: 127rd

April 2016


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Introduction……………………………………………..……... 3

Practice development…….…………………………………….. 1 3

Questionnaire.……………………………………………...…... 1 5

Conclusions……………………………………………………. 1 6

Sources of consultation………….……………………………… 1 7

ndice


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Objective: Analyze and solve circuits areconfigured in series by applying theconcept of the voltage divider.

provided by the laboratory

1. Digital Multimeter.

1. Source variable DC voltage.

1. Function Generator.

Introduction

1. Voltage divider

The voltage Vs (t) is divided into voltages that fall into the resistors R1 and R2.

This formula is only valid if the output v2 (t) is open circuit (no current flows through

the terminals where measured v2 (t)).

by students:

4 points gator-gator.6 point banana-alligator

1 breadboard.

2 resistors 1KOhms to 1/2 W

1 resistors 470Ohms 1/2 W

1 Resistance 2.2KOhms 1 / 2w

1 Potentiometer 5kOhms

1 capacitor 10uf 25V

1 Transformer voltage 12Vrms to 1A

connecting wire for breadboard.


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The voltage divider is very important in a basic circuit, and for the exploration of the

above calculation with multiple values, knowledge can provide a large number of

practical applications of circuits. A practical consideration is that a large value of

R2 compared to R1, will give a higher output voltage. But if your load resistor RL is

smaller than R2, decrease the output voltage and need the power supply a higher

current and total power. On examination, you find that for a given set of values of

the voltage divider (R1 and R2), get more power to the load if you lower the load

resistance RL, but this is at the expense of increased current and power from

power supply.

Note: To prevent the occurrence of a short circuit, the divider resistors with zero

default value is set to value 1, when the voltage and load resistance will default

value 1000 is changed. They can be again changed back to zero if you want to

explore the effects of short circuits. The unit indicated resistance is the ohm, but

are more common kilo ohms, although of course the calculation is the same.

More information

A voltage divider is a simple circuit that delivers the voltage of a source Betweenone or more connected impedances. With only two resistors in series and an inputvoltage, voltage Get UN equivalent to a fraction of the output can be input. Voltage

dividers son one of the most fundamental circuits in electronics.Circuit

A voltage divider is connected requires a voltage source through two resistors inseries. It is possible that the voltage divider is drawn in different ways, but must beessentially the same circuit.

We call the nearest resistance to the input voltage (Vin) R1 and to the nearestground resistor R2. The voltage drop across R2 is our output voltage (Vout), this is


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the voltage resulting from our circuit, which as already mentioned is a fraction ofour input voltage.

Equation

The voltage divider equation assumes that three values of the above circuit areknown: the input voltage (Vin), and both the resistance values (R1 and R2). Given

these values, we can use this equationto find the output voltage (Vout):

This equation states that the output voltage is directly proportional tothe input voltage according to the ratio of R1 and R2.

simplifications

There are some generalities that must be taken into account whenusing voltage dividers. These are simplifications that make theevaluation of a voltage divider circuit is a little easier.

First, if R1 and R2 are equal, then the output voltage is half that of theinput. This is true regardless of the values of the resistors.

If R 2 is much greater than R1, then the output voltage will be veryclose to the entrance. There will be very little voltage across R1.

Furthermore, if R2 is much smaller than R1, the output voltage will bevery small compared to the entry. Most of the input voltage is throughR1.


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Applications.

The voltage dividers have a lot of applications, are among the most

common electrical circuits that engineers use. These are just some ofthe many places where we find voltage dividers:

Potentiometers

A potentiometer is a variable resistor that can be used to create anadjustable voltage divider.

Inside there is a single potentiometer resistance anda needle which two short resistance and moves to adjust therelationship between the two halves. Externally there are usually threepins, two pins connected to each end of the resistor, while the third is

connected to the needle potentiometer.

If the pins of the ends are connected to a voltage source (one toground and the other Vin), the output (Vout) on the central pin mimic avoltage divider. Rotating the needle to the end of the potentiometer inone direction, the output voltage can be zero; turning to the other side,the output voltage will approximate the input; If the needle is in themiddle position means that the output voltage will be half that of theinput.


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Any required load current will also have to run through R1. The currentand voltage across R1 produce energy, which is dissipated as heat. Ifthis energy is higher than can be tolerated resistance (usually between⅛ W and 1 W), the heat starts to be an important problem, which could

melt resistance.This does not even mention it would be inefficient power source withreduced voltage divider. Basically, you should not use a voltage divideras a power source for anything that requires even a small amount ofenergy. If you need to reduce a voltage for use as a power source, it isrecommended to check the voltage regulators or power sourcesvariables.

Let’s analyze a simple parallel circuit, determining the branch currents through

individual resistors:

Knowing that voltages across all components in a parallel circuit are the same,

we can fill in our voltage/current/resistance table with 6 volts across the top row:

Using Ohm’s Law (I=E/R) we can calculate each branch current:


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Knowing that branch currents add up in parallel circuits to equal the total current,

we can arrive at total current by summing 6 mA, 2 mA, and 3 mA:

The final step, of course, is to figure total resistance. This can be done with

Ohm’s Law (R=E/I) in the “total” column, or with the parallel resistance formula

from individual resistances. Either way, we’ll get the same answer:

Once again, it should be apparent that the current through each resistor is

related to its resistance, given that the voltage across all resistors is the same.

Rather than being directly proportional, the relationship here is one of inverse

proportion. For example, the current through R1 is twice as much as the current

through R3, which has twice the resistance of R1.

If we were to change the supply voltage of this circuit, we find that (surprise!)

these proportional ratios do not change:


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The current through R1 is still exactly twice that of R3, despite the fact that the

source voltage has changed. The proportionality between different branch

currents is strictly a function of resistance.

Also reminiscent of voltage dividers is the fact that branch currents are fixed

proportions of the total current. Despite the fourfold increase in supply voltage,

the ratio between any branch current and the total current remains unchanged:

For this reason a parallel circuit is often called a current divider for its ability to

proportion—or divide—the total current into fractional parts. With a little bit of

algebra, we can derive a formula for determining parallel resistor current given

nothing more than total current, individual resistance, and total resistance:


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The ratio of total resistance to individual resistance is the same ratio as individual

(branch) current to total current. This is known as the current divider formula, and

it is a short-cut method for determining branch currents in a parallel circuit whenthe total current is known.

Using the original parallel circuit as an example, we can re-calculate the branch

currents using this formula, if we start by knowing the total current and total

resistance:


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REVIEW:

Parallel circuits proportion, or “divide,” the total circuit current among

individual branch currents, the proportions being strictly dependent upon

resistances: In = ITotal (RTotal / Rn).

1) Checking voltage divider analysis in CD.

For the circuit of figure 3.

Figure 2. Circuit that shown the voltage divider analysis (simulation)

Analytically we obtained voltage and current values as follows:

1º. We reduce R3 y R4 because these resistors are in parallel.

= 3||4 =

1

11000

+ 1560

= 358.97

And now, we have a circuit with resistors connected in serie that we can solve withvoltage divisor.

We takes RT as the resistors in serie.

Development


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= 1 + 2 + = 1Ω + 170Ω + 358.97Ω = 1828.97 Ω

We know that V1= VT = 10 V.

2° We use in each resistor the next theorem.

=

And then substitute the values.

1 =(10) (1000)

1828.97= 5.467

2 =(10) (470)

1828.97= 2.5697

3 = 4 =(10) (358.97)

1828.97= 1.96

Finally, we observed that

2 = 1 + = 2.5 + 1.96 = 4.53

3 = 1.96

3 =3

3=

1.96

560 Ω= 3.5

4 =4

4=

1.96

1000 Ω= 1.96

The figure 2 and 3 shown the circuit simulation,and we compare the values, which they are toosimilar, it the same with the measuring values.

Fig. 3


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Measurements Theoric Value Measured Value Simulated Value

V1

10 V 9.9 V 10 VV2 4.53 V 4.55 V 4.54 V

V3 1.96 V 1.97 V 1.96 V

VR1 5.46 V 5.44 V 5.47 V

VR2 2.56 V 2.57 V 2.57 V

VR34 1.96 V 1.97 V 1.96 V

IR3 3.5 mA 3.57 mA 3.50 mA

IR4 1.96 mA 1.96 mA 1.96 mAIRT 5.55 mA 5.54 mA 5.46 mA

Table 1. Values of currents and voltage teoric.

1. What should the existence of the error of the measured value against thecalculated?

It is because when we refer to the calculated values we consider an ideal testingenvironment, however, the environment in which we work is the real, which is whythere is such deviation values, because of measurement tools, temperature frictionand so many factors that determine the variation.

2. What is the value of the voltage divider circuit for analysis?

The voltage divider is used when elements are connected in series and a voltagesource. It is also useful when you want to know the voltage between two resistors.

3. You can extend the div ider circuit voltage to a greater number of

resistors?

Yes, it can

Questionnaire


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4. If the voltages at each node were required for speci fic defaults, what

should be done to get these values?

Place a resistor or resistors, the arrangement of electrical resistance valuecomplies with the law of ohm and voltage division to match the voltage betweennodes that is connected.

García Barrera Guadalupe:

It is my opinion, it was a very useful practice to reaffirm the things that are alreadyknown, to find possible failures that may continue to have, is something nicealways descrubir nuesvas things and as measured by different methods and as the

current flows in each branch, is very nice, and very interesting artwork, to learnhow the devices work as they were creating the beginnings to cash them.

María del Carmen García Macías:

Voltage dividers are very useful because they facilitate the calculation of voltages,a lot thanks to this little theorem calculations are simplified. In the practice circuitwe observed that the resistors have to be connected in serie, if is not thatconfiguration, maybe we can reduce the circuit.

Now we have a lot of methods to obtain the voltage and currents values.

Oscar Arturo García Ortega:

In this practice we saw that was a divider circuit voltage and a divider currentcircuit.

We learned that these two expressions provide us in some cases, analysis ofelectrical circuits and help us calculate the current and voltage in each of the circuitelements in an easier and faster way.

The voltage divider serves to find the voltage within a set of series resistors, whilethe current divider allows us to find the current in a resistors in parallel.

Conclusions


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Renny Tovar y José Romero. (2007). Laboratorio de circuitos electricos. Venezuela:COMISIÓN ACADÉMICA DEL PROGRAMA NACIONAL DE FORMACIÓN ENELECTRICIDAD

https://learn.sparkfun.com/.../voltage-current-resistance-and-ohms-law

Sources of consultation
https://learn.sparkfun.com/.../voltage-current-resistance-and-ohms-lawhttps://learn.sparkfun.com/.../voltage-current-resistance-and-ohms-lawhttps://learn.sparkfun.com/.../voltage-current-resistance-and-ohms-law

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