Doe, John - Lab 1 Report

ID: 1234567

Han Q. Le(c)

Part Intro -  Basic of bread board and lab instruments

0.1 Bread board assembled

The breadboard (BB) that was distributed is ready to be used as is, without any need to do anything. True or False? explain your answer. Take a picture of your assembled breadboard with a taped label of your name, student ID (for credit).

1.1 Answer

I can just type my answer here (* this is where you write your answer  *)

0.2 BB property

The holes on the BB are only for holding the legs of circuit elements, and to connect one circuit element to another, we need to wrap the wire on their legs together like the picture beside. True or False. Explain your answer.

1.2 Answer

There is no need for wire wrapping of component legs because the BB

0.3 BB property: column

All the holes belonging to a column of a breadboard (the holes running along the length of the board) are:
a.	Electrically connected together
  b.	Electrically isolated from each other
                       c.	Electrically connected together for some columns and isolated for other columns
                       Explain your choice. You can insert a drawing or a sketch

0.4 BB property: row

All the holes belonging to a five-hole row of a breadboard (the five holes running parallel to the width of the board) are: 
a.	Electrically connected together
  b.	Electrically isolated from each other
                  c.	    Electrically connected together for some rows and isolated for other rows
 Explain your choice. You can insert a drawing or a sketch

0.5 Power supply to a BB

To supply electrical power for the breadboard in this course, we connect the binding post to the wall plugs. True or False?

0.6 DC power supply

If we do work in the Undergraduate Electronics lab, what instrument do we use to get DC power for the breadboard? What do you plan to use at home?

Part A  -  Key concept of the Lab: electrical current

A.1 Electrical current necessity

If there is absolutely no current flowing - zero, nada, in a circuit, do you think the circuit is operative, in other words, is it doing some function that it is designed for?

A.2 About electrical current

What is the nature and the definition of electrical current? (see the app about electrical conduction)

A.3 Seeing current?

Can we visually see an electrical current directly?

A.4 Measuring current

If we want to know the value of the current in one path of a circuit, what should we do?

A.5 LED as current indicator

What is a simple solid state 2-terminal device that we can use to visually see the evidence of a current flow? (not to measure it, but can see roughly the magnitude)

Part B  -  Study R-LED DC circuits
Note: use App Lab 1 RLED circuit

B.1 Basic resistor circuit

We want to build the circuit below (on the left - no LED inspite of the label, which will be added later). Which BB wiring configurations on the right represent the correct circuit?

Figs. 1.1 and 1.2

B.2  Measuring current through a resistor

For the circuit in 3.2, (Subscript[v, S])~ 3 - 3.5 V (one can use 2 x 1.5 V battery). Use Ohm’s law to estimate the current. If you have the instrument or are in a lab, then measure the current, compare with your calculation.

B.3 LED circuit

Figure on the right shows 5 possible LED wiring configurations.  For the LED (circle), the red square indicates its anode (positive terminal, long leg) and the blue, its cathode (negative terminal, short leg).

The question is: which of the 5 LED wiring configurations above will work, i. e. emit light. In fact, if you wire all 5 as shown, you will see that none of the LED will light up, and the power supply will indicate it is short-circuited. By removing just one wire, you will see that the power supply is no longer shorted, and some LED’s will emit light. Do not do this if you use a battery supply or a power supply without voltage control and current limiter, identify and remove the shorted circuit wiring first.

Figs. 2.1 and 2.2

For actual lab work and report:
- write an explanation why some wiring configurations work and some don’t.
- build only a correct one;
- adjust the voltage such that the current is ~ between 15 - 20 mA. Measure the voltage. Do it again with LED current between 2-5 mA.

B.4 Resistor and LED circuit

Figure below shows 4 possible wiring configurations for the schematic on the left. For the LED (circle symbol), the small red square indicates its anode (positive terminal, long leg) and the blue, its cathode (negative terminal, short leg). The resistor and the LED are supposed to be in series.

1- The question is: which of the 4 R-LED wiring configurations will work, i. e. the LED will emit light.

2- For actual lab work and report: Select one that works. Start with a 100-Ω resistor, set the voltage such that you see the LED is bright (make sure it is bright enough to take picture). Change the resistor for the following value: 200 Ω, 470 Ω, and 1 kΩ. Report what you observe and explain why.

3- If you have measurement instruments, set the voltage with initial resistor = 100 Ω. Measure the LED current, adjust the voltage such that the current is between 15 - 20 mA (a few mA higher or lower is OK, don’t worry too much). Then, reduce the current to ~3-6 mA, measure the source voltage again and report.

Figs. 3.1 and 3.2

B.5 Current limiter

We build and measure the circuit, but have we thought why it is designed to be so? Why an LED (to see the light, of course), but why a resistor? What is it for? (hint: Run the app and see what happens when we short across the resistor. We can do that on the circuit board, and the LED would have the last shining of moment of its life).

Part C  -  Serial and parallel current distribution

C.1 Household lectrical wiring

Is the electrical wiring in your house serial or parallel?

C.2 Serial vs. parallel

Which wiring diagram(s) in 4.3 represent parallel circuit in Fig. 4.1, and which one(s) represent serial circuit 4.2?

Fig. 4.1

Fig. 4.2

Fig. 4.3

C.3 Build serial and parallel LED circuits

Select and build one parallel circuit as illustrated in Fig. 4.3, using LED of the same color, and one serial circuit in Fig.4.3 using LED of different colors. Measure the net voltage and current of each circuit. Take picture and report. Use the a current value so that the LED is visible, but not excessive (to avoid degradation). Which one has high voltage, low current and which one has low voltage, high current.

Part D  -  Parallel current distribution

Build circuit 5.1 with 4 different LED colors. Choose different resistance values such that all the LED currents are ~ 10 -15 mA. Measure each LED current. Measure the total current of all 4 LED subcircuits and verify that:
total current = sum of all LED currents. This is known as _____ law. (KCL)

Fig. 5.1

Summary and conclusion

(*  write what you learn about electrical current, parallel and serial, and anything else about circtuit that you learn in doing this Lab. *)

END