Download 1 LAB 2: Circuitos de Corriente Directa (DC) PARTE I OBJECTIVES

LAB 2: Circuitos de Corriente Directa (DC)
PARTE I
OBJECTIVES
•
•
•
To learn to design and construct simple circuits using batteries, bulbs, wires and
switches.
To draw circuit diagrams using symbols
To understand the measurement of current and voltage using microcomputerbased probes
OVERVIEW
In the following lab you are going to discover and extend theories about electric charge
and potential difference (voltage) and apply them to electric circuits. You will use a
battery, a device that generates an electric potential difference (voltage) from other forms
of energy. The type of battery you will use is called a chemical battery because it
converts internal chemical energy into electrical energy. Alternatively you could also use
the DC power supply that comes with the instrumentation.
As a result of a potential difference, electric charge is repelled from one terminal of the
battery and attracted to the other. However, no charge can flow out of the battery unless
there is a conducting material connected between the two terminals. If a light bulb is
connected between the two terminals of the battery, the flow of charge will cause the
light bulb to glow.
In this lab, you are going to explore how charge flows in wires and bulbs when energy
has been transferred to it by a battery. You will be asked to draw circuit diagrams and use
microcomputer-based probes to measure and graph voltages and current as a function of
time.
ACTIVITY 1:
Using a battery, one wire and one bulb connect the wire and the bulb to the battery so as
to cause the bulb to glow. There are two arrangements that work and two that do not
work. Draw circuit diagrams for the arrangements that work.
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ACTIVITY 2:
You will now explore models for current in a circuit. Use any one of the arrangements
above. Which of the following models you think best describes the flow of current in the
circuit.
Model A: There is an electric current from the top terminal of the
battery to the bulb through wire 1, but no current back to the base
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of the battery through wire 2, since the current is used up in
lightning the bulb.
2
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Model B: There is an electric current in both wires 1 and 2 in a
direction from the battery to the bulb.
2
1
Model C: The electric current is in the direction shown, but there is
less current in the return wire (wire 2), since some of the current is
used up in lighting the bulb.
2
1
Model D: The electric current is in the direction shown, and the
magnitude of the current is the same in both wires 1 and 2.
2
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ACTIVITY 3:
Measuring potential difference (voltage) and current in a circuit consisting of a battery, a
switch and a bulb. You will be asked to use the current sensor and the voltage sensor for
this purpose. You must remember that the current sensor is always connected in series
with the bulb through which you wish to measure the current and the voltage sensor is
always connected in parallel across the bulb to measure the voltage.
Switch
Voltage Sensor
Curre nt Sensor
With the circuit connect as shown in the figure, plot graphs of voltage as a function of
time and current as a function of time. Keep opening and closing the switch in order to
study its effect on the current and voltage that you are measuring. What do you conclude?
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ACTIVITY 4:
Repeat activity 3 but with two bulbs connected to the same battery. Draw the circuit
diagram and proceed to measure the current through each bulb (use two current sensors if
you wish) and the voltage across the battery. What do you conclude?
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PARTE II
Propósito:
Los Circuitos proveen la base para toda la electrónica de instrumentación. En este
laboratorio, tendremos la experiencia en construir circuitos, midiendo la diferencia en
potencial a través de los resistores y la corriente que fluye a través del circuito.
Introducción
Los resistores son componentes que tienen un valor de resistencia al flujo de corriente
que puede ser utilizado para bajar el potencial o la misma corriente. Por la ley de Ohm, el
voltaje a través de un resistor es directamente proporcional a la corriente que pasa por
este.
V = IR
(1)
Donde V es el Voltaje que se mide en Julios/Columbios, I es la corriente a través del
resistor que es medida en Columbios/segundos que es la definición para un Amperio (A)
y R es el valor de la resistencia medida en ohmios (Ω).
Cuando los circuitos son conectados en serie, como lo muestra el circuito ilustrado en la
figura 1. Por la ley de Kirchhoff’s que nos dice que la suma de los voltajes a través de
una malla son igual a cero.
R1
I
R2
V1
Figura 1. Circuito DC en Serie
Entonces por el diagrama anterior podemos decir que la corriente es la misma para todo
el circuito, y que la suma de los voltajes en los resistores debe ser igual al voltaje de la
fuente tal como lo ilustran la ecuaciones 2 y 3.
V1 = VR1 + VR 2
V1 = IR1 + IR2
(2)
(3)
Cuando los resistor son puestos en paralelo, como el circuito que se muestra en la figura
2. la caída en potencial para cada resistor es la misma y la corriente se dividen entre los
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resistores. El valor de la corriente fluyendo por cada resistor es el voltaje aplicado
dividido por el valor de la resistencia.
V1 = VR1 = VR 2
I = I1 + I 2
V1
V
V
= R1 + R 2
R eff
R1 R2
(4)
(5)
(6)
1
1
1
= +
R eff R1 R2
V1
(7)
R1
R2
Figura 2. Circuito DC en Paralelo
Procedimiento:
Examine los resitores examines las banda de colores para saber que valores tienen los
resistores.
Ensamble los circuitos tal y como lo ilustran las figuras 3 y 4, coloque los sensores de
voltaje y corriente suplidos por el instructor. Ejecute el programa Data Studio para poder
capturar la data recogida por los sensores, luego llene la sección de datos ilustrada
adelante.
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R1
R2
V1
R3
1kohm
Figura 3. Ciruito DC en Serie
R1
V1
R2
R3
Figura 4. Circuito DC es Paralelo
Reporte de Laboratorio
A. Resistores en Serie
Valores
los
resistores
R1
_______________
R2
________________
R3
__________________________
Fuente de Voltaje V1 ________________
Resistencia Equivalente Re _______________
Corriente I ______________
Caida de Voltaje a traves de los resistores
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VR1 _______________
VR2 _______________
VR3 _______________
Medidas Experimentales
I _______________
I1 _______________
I2 _______________
I3 _______________
B. Resistores en Paralelo
Fuente de Voltaje V1 ________________
Resistencia Equivalente Re _______________
Corriente I _______________
Corriente a través de los resistores
I1 _______________
I2 _______________
I3 _______________
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