Week 3 Blog

Week 3

1. Compare the calculated and measured equivalent resistance values between the nodes A and B for three circuit configurations given below. Choose your own resistors. (Table)

Circuit	A	B	C
Measured	83.5 ohms	4.76k Ohms	4.99k ohms
Calculated	84 ohms	4.75k ohms	5k ohms

2. Apply 5V on a 120 Ω resistor. Measure the current by putting the multimeter in series and parallel. Why are they different?

~~When in series you can read the current, because the resistance isn't being bypassed.

~~When in parallel you can't read the current, because the resistance is being bypassed.

3. Apply 5 V to two resistors (47 Ω and 120 Ω) that are in series. Compare the measured and calculated values of voltage and current values on each resistor.

Measured Voltage	Measured Resistance	Measured Current	Calculated Current	Calculated Voltage
3.61V	120 ohms	29.81 mA	29.94 mA	3.59 V
1.39V	47 ohms	29.85 mA	29.94 mA	1.41 V

Table: showing the values we obtained from the circuit in SERIES

4. Apply 5 V to two resistors (47 Ω and 120 Ω) that are in parallel. Compare the measured and calculated values of voltage and current values on each resistor.

Measured Voltage	Measured Resistance	Measured Current	Calculated Current	Calculated Voltage
4.78V	120 ohms	37.35 mA	41.67 mA	5.0004 V
4.78V	47 ohms	140.3 mA	148.05 mA	4.9975 V

Table: showing the values we obtained from the circuit in PARALLEL

5. Compare the calculated and measured values of the following current and voltage for the circuit below: (breadboard photo)

Calculated Current	Measured Current
1.98mA	2.03 mA

Resisters	Measured Voltage	Calculated Voltage
1.2 kohms (vertical)	0.724 V	0.704 V
1.2 kohms (horizontal)	0.853 V	0.833 V

Picture of the circuit with 5v from power supply

Same circuit as previously pictured, just a different angle

6. What would be the equivalent resistance value of the circuit above (between the power supply nodes)? 

~~The equivalent resistance value is calculated by taking the 5V and divding it by the calculated current which is 1.98mA. For us the equation will be 5V/0.00198A = 2525.25 ohms or 2.52525 K ohms.


7. Measure the equivalent resistance with and without the 5 V power supply. Are they different? Why?

~~The equivalent resistance with the power supply can't be found, because the multi-meter will display "OL" which means overload. This happens because the multi-meter has its own voltage and so does the power supply. These 2 voltages will trick the multi-meter and it won't be able to find the equivalent resistance.

~~The equivalent resistance without the power supply can be found, and that's because only a single voltage coming from the multi-meter is effecting it. The equivalent resistance from the multi-meter is 2.6 kohms, which is accurate based on previously calculated equivalent resistance (see question 6).

8. Explain the operation of a potentiometer by measuring the resistance values between the terminals (there are 3 terminals, so there would be 3 combinations). (video)

~~When the potentiometer is turned to 0 ohms there will be no voltage because there is no resistance, but if the potentiometer is turned to any ohms greater than 0 then the voltage would be 5V, with a differing current.

Video demonstration of how the potentiometer works

9. What would be the minimum and maximum voltage that can be obtained at V1 by changing the knob position of the 5 KΩ pot? Explain.

~~When the knob is turned to as low as possible the minimum value will be close or at 0V. When the knob is turned to its highest position the maximum value will be at or around 5V.

10. How are V1 and V2 (voltages are defined with respect to ground) related and how do they change with the position of the knob of the pot? (video)

Video demonstration on finding the voltage in a circuit with a resistor and a potentiometer

11. For the circuit below, YOU SHOULD NOT turn down the potentiometer all the way down to reach 0 Ω. Why?

~~If you were to turn the potentiometer all the way down to 0 you would short your circuit, because there would be no resistance in your circuit.

12. For the circuit above, how are current values of 1 kΩ resistor and 5 KΩ pot related and how do they change with the position of the knob of the pot? (video).

Video demonstration of measuring current over a resistor and potentiometer

13. Explain what a voltage divider is and how it works based on your experiments.

~~A Voltage Divider is a simple circuit that will take a large voltage and turn it to a smaller voltage. In this experiment the potentiometer itself is a voltage divider.

14. Explain what a current divider is and how it works based on your experiments.

~~A Current Divider is a linear circuit that produces a current output (Ix) that is a fraction of its input current (It). It works for our experiment, because of the resister value. When the potentiometer's resistance decreases the current will go up.

Week 2 Blog

Week 2

1.  The role of the A/B switch is to give you 2 different power supplies that can be used at the same time in series mode or just using one at a time for parallel mode. Depending on what mode you are on B could be helping A like in series if each switch is on 15V, then the total voltage will be 30V. If you are in parallel mode then B will take the voltage of A, so if A is on 5V so will B, but the voltage total will be 5V.

2. The current specification of each channel reads either .5 amps or 4 amps. This means that the current coming out of the power supply is either .5 amps or 4 amps, depending on which current you chose to use.

3.  Video explanation on how the A and B channels work on the power supply unit

4. Generating 30 volts with the power supply

Picture of the power supply setup used to find +/- 30 volts

DMM reading of roughly 30 volts

5.  Generating -30 volts with the power supply. We used the same set up as above just switched the location where we measured.

DMM reading of roughly -30 volts

6. Generating 10 volts and -10 volts at the same time

Power supply setup to display +/- 10 Volts

DMM reading of roughly 10 volts

DMM reading of roughly -10 volts

7.  Video showing how removing current affects the circuit. When the current knob is turned almost entirely to the left (CCW) the LED turns on and the voltage drops to 0 volts. Therefore, the DMM reads 0 amps for the current as well. This is a simple application of Ohms law.

V=I x R

If 'I' is zero V is also 0

8. The fuse for the power supply is located at the back of the power supply where you would plug in the power cord. It is used to protect the user and the machine from damage.

9. The fuse for the DMM is located at the bottom left of the input/output plugs. The fuse is used as a backup to the user and machine to make sure that they don't get hurt when there is too much voltage.

10. 2W is used more for Lead Resistance and has some limitations compared to the 4W. The 4W (Kelvin) Resistance is used more for low resistance measurements. It also has less limitations than the 2W when being used for low resistance. 

11. To measure a current using the DMM we would move the positive cord to the right of the fuse instead of its original position of being above the fuse. We would also keep the negative cord in its normal position which is top diagonal of the fuse.

Week 1

Week 1

1.     The class format on a tri-weekly format consists of:

Table 1: A Weekly Outline for Circuit Lab

Weekly Schedule for Circuit Lab
Time	Monday	Outside of Class	Wednesday	Friday	Outside of Class
8:00 am	Quiz Discussions	Respond to comments	Lab		Finish blog entries Comment on 2 blogs Take-home quiz
8:30 am	Lab intro
8:45 am	Lab
9:00 am				Blog Commenting
9:15 am
9:30 am				Blog Discussion
9:45 am	Wrap it up!		Wrap it up!

Quizzes (15) make up 45% of the class, blogs (15) reports 30%, midterms (2) 10%, and the final exam (1) 15%

2.     Important safety rules:

•        Do not work alone when working with energized electrical equipment.
•         Make sure the power is off when assembling a circuit. Remember that capacitors store charges and are to be handled with caution even after the power source is removed from the circuit
•         Never touch electrical equipment while standing on a wet or metal floor. In addition never touch electrical equipment with wet hands.
•        When measuring data in live circuits be sure to put one hand behind the back to prevent current from flowing
•        Wearing jewelry on your wrists or hands can be hazardous and it is advised to remove them or use added caution when wearing them.
•        Never lunge or grasp at falling circuit components, whether they are live or not, circuit components have metal leads that could pierce your skin.
•        Never touch two pieces of equipment at the same time. This completes loop and allows current to flow. To be safe never touch any aspect of the circuit with your bare hands, it could deliver a shock. In addition, some components release high levels of heat, which can cause burns.
•     Ask the instructor before hooking up the circuit to power.

3.  Current is the lethal force that will kill you. Low levels of current can be completely benign or cause a small tingly sensation; this is at level of .001 amps to .01 amps. Current higher than .01 amps can cause the muscle paralysis that forces the person being shocked to continue to hold onto the current source. This is dangerous because prolonged exposure can make breathing difficult and painful shock. When current is .1 to .2 amps death occurs. Interestingly enough current over .2 amps isn’t instantly lethal. There is enough current to keep you alive. This is because the heart is in a clenched state that doesn’t allow for ventricular fibrillation to occur, but the current causes severe burns and causes you to stop breathing.

4. Link for video demonstration on how to read resistor color code (https://youtu.be/Sc0sTWF0eUI)

5. Tolerance is the margin of error that a resistor's has. In example if a '100' ohm resistor had a 5% tolerance, that means when the resistor is applied to a circuit its actual value could range by 5%. Therefore are 100 ohm resistor could produce values from 95 ohms to 105 ohms (+/- 5% of 100 ohms)

6. A chart proving that all of our resistors were in the tolerance range:

Resister Band Value (ohms)	Tolerance	Range (ohms)	Measured Value (ohms)
160 ohms	5% (0.05)	152 ohms-168 ohms	158.31 ohms
1500 ohms	5% (0.05)	1425 ohms-1575 ohms	1503.22 ohms
67 ohms	None this was 5 band and the 5th band color was white so there is no tolerance for this specific resister.	67 ohms (because it has no tolerance, its range can fluctuate up and down, it’s fixed)	67 ohms
27.2 ohms	10%	24.48 ohms -29.92 ohm	27 ohms
20.1 ohms	10%	18.09 ohms - 22.11 ohms	20 ohms
20.2 ohms	5%	19.19 ohms - 21.21 ohms	20 ohms
25.2 ohms	10%	22.68 ohms - 27.72 ohms	25.1 ohms
39.1 ohms	5%	37.145 ohms - 41.055 ohms	39 ohms
2200 ohms	5%	2090 ohms - 2310 ohms	2202 ohms
100 ohms	5%	95 ohms - 105 ohms	101 ohms

7. When using a multimeter to measure the voltage and current two different techniques need to be used. When you are measuring the current you need to break the current loop and attach the multimeter where you broke the current loop. This is because the current needs to travel through the multimeter. When measuring the voltage across a resistor you touch each lead of the resistor with the multimeter. You do this to observe how much voltage a particular component is using.

8. The power supply will give you 2 different options of voltages. The first would be the fixed position all the way to the left. This position will give you a constant 5V, and no you cannot change the voltages of this position, it will always be 5V. The other option is 0.24V coming from both the A and B power supplies. Yes, you can change this voltage higher or lower depending on what voltage your looking for. Also applying current will help to get more voltage out of these 2 power supplies.

9. Video and Picture Demonstration for circuit results (https://youtu.be/yTZoMPjd1G8)

Picture of Group 10 measuring the voltage through a resistor

10.

A table demonstrating how Ohm's Law can be used to find calculate the value of a resistor

Picture showing the setup used to measure values for a particular resistor

11. Video Demonstration for Rube Goldberg Circuit (https://youtu.be/z1NWg-PpW30)

12.

A schematic diagram of the Rube Goldberg circuit

13. You could use this motor with a wheel attached to it to charge a capacitor. The wheel would have an LED attached to it which would spin with the DC motor. When the LED passes directly in front of a light sensor the current can be sent through and charge a capacitor which would then release the charge to push a ball.