High Speed Photography with Electromagnetic Gun (Working with electrons)

High Speed Photography with electromagnetic gun

Section 1: My thought begins with building an electromagnetic gun

The thought I had to make an electromagnetic gun is generated from my engineering intuition. I once said in the classroom that I wanted to make an amplifier, a voice amplifier. This was because I want to finish this course with a design with the procedure from circuit design to the actual physical components design. I used to design an amplifier and I used to want to use this chance to make it true. However, due to it will be just an amplifier (not fun), I abandaned that idea. After a Google search in my mind about how to use my knowledge to start a circuit design, I came up with the idea about the Electromagnetic Gun.

The electromagnetic gun is made by many circuit components: transistors, diodes, capacitors, ziodes, resistors, coils and of course the power supply. I found many versions for circuit design of electromagnetic guns, and I ended up with using the circuit diagram below following the Youtube video.

Circuit diagram of electromagnetic Gun

 

Version 1: Prototype

Everything starts with prototype that tries out the accessibility of the circuit design. I started by getting all the required materials in the circuit and built it. Every component I got was from Taobao and I followed exactly the same procedure on the Youtube video: here it comes the prototype.

Prototype 1: electromagnetic gun

I powered it up with four 5V batteries which can help me charge the capacitor really fast. The digital screen is basiclly a voltage meter which shows how much voltage is charged across the capacitor. Two bottoms are designed as the charging botton (yellow one) and the other was the firing botton (red one). All the devices are put in a bubble box for safety reasons. I recorded one video for the firing (it is in slow motion).

After successfully tested all the components, I started to think about what can I do with it. I received many wonderful comments from follows in IMA, and one advice among all of them was doing a high speed photography.

Section 2: Let’s start High Speed Photography

“Bullet Through Apple” (1964), by Harold E. Edgerton. Courtesy of the M.I.T. Museum.

“Bullet Through Apple” (1964), by Harold E. Edgerton. Courtesy of the M.I.T. Museum.

Inspired by the picture searched online and from the advice by Rudi and Cindy, I want to test whether the gun was powerful enough to break something like the a plastic bag filled with powder so we can capture some wonderful pictures like the one above.

I bought one kind of stive (an edible material in cooking) (shown below) and some very thin plastic bags to test. The test result is not good. It turned out I cannot impale the bag with dust inside, even it only contains a small part of it.

The edible dust (Soda powder)

The hole on the plastic bag

The dust in the bag

Test by putting the whole bag directly on the coil gun, but it still cannot penetrate

When I wanted to increase the power of coil gun (try to penetrate the powder bag), I increased my charge up to 250V (I nevered did this large), the circuit burned when I fired. I heard a very large sound and saw a spark. The circuit stop working. I could not charge up the circuit any more. I had to come up with alternatives (4 days till presentation).

After carefully examing the circuit, we found that it was due to the burn down of one transistor. I had to redo and reconstruct the whole circuit. The picture below is my orginal “fire button”, my voltage meter and the transistor. I took them off kept as a souvenir lol.

Section 3: more experiment on High speed photography

After fixing the circuit problem I had before, I continue on my experiment. This time, instead of trying to penetrate something, I just wanted to see some effects of impact. Thanks to the help from professor Rudi, I set up the my equipment as shown in the figure below. We used one adurino and two relays to control the gun and the camera. The light there is to provide enough tight for the photography since we would be shootting under 1/4000 shutter speed. After several trials, I adjusted a relatively good delay time between two devices (1500us) and took some photos. There are many points one should be attention to for the camera setting here:

  1. The shutter speed of the camera needs to be as fast as possible. For Canon 6D, the fastest we had is 1/4000. With a faster shutter speed, you will be able to capture faster objects clearly.
  2. Provide enough lights. Although the large aperture can give more incoming lights, it’s far not enough. A strong flash light or a consistant light source (like what I had) is very necessary.
  3. Switch the focus mode to manual focus. Auto focus will waste 1 sec in focusing every time it shoots and we cannot allow that. Adjust the focus to a proper focus distance and set to manual setting.

Let me also put on some pictures when I did countless experiments.

 

 

 

The photography setting

 

Fail 1: Loss focus

Fail 2: Bad timing

 

Fail 3: Bad timing

Fail 4: Bad timing

Succuss

The synchronous between gun and camera needs to be adjusted carefully. For different energy in the capacitor, we need different delay time. For example, 100V —- 1500us, 150V —- 17500us and so on. This number need countless trials and fails, so if someone in the future wants to do this again, don’t give up.

Section 4. My Work

 

After countless trials (more than 300 pictures), I had some successful pictures. Please enjoy them below.

Group 1-1

Group 1-2

Group 2 – 1

Group 2 – 2

Group 3 – 1

Group 3 – 2

Group 4 – 1

Group 4 – 2

Group 5 – 1

Group 5 – 2

Group 6

In the above, I put on 6 groups of photos. One group of photo (besides group 6) contains two pictures. The first one is 1 second before the impact on the dust and the second one is the impact effects. If you can put two pictures together for comparison, you will see the effects. For group 6, I am shooting a jelly. The picture recorded the exact moment when the bullet get inside the jelly.

As you can see, I chose 3 different materials: dust, potato chips and jelly. I chose them because my gun is not powerful enough to penetrate something like an apple or a bottle.

Section 5: Conclusion and some thought

I believe high speed photography is a very charming category in the photography family. It can capture the moment that cannot be seen by human eyes and that’s what makes it unique. However, it’s unique and very hard to capture. You have the contrains in the camera side, the gun side, the lighting device. Despite every device is properly set, you still need many tries before you can actually see something.

I didn’t start this project considering I will do high speed photography, so I just had about 3 days to do the shooting adjustment. If I had more time or I made the decision earlier, I would definitely have some more beautiful pictures. Next time someone try to do this, he should keep a good recording of the setting of each shooting: how many charges are in the capacitor, what’s the distance between the gun and the camera, how many microseconds should the delay be…… If one wants to use a more powerful gun (such as a real gun), the shutter speed might need to be quicker so you might need a more professional camera. This is a difficult task both from the aspect of device constrains, and from the aspect of the efforts you need to put on.

I considered my work in this project is satisfactory but far from a good work. This is a very wide aspect of photography and so many artists put years of work into it. This even deserves an entire class to introduce it. I learned a lot from this project and during the whole process. I have writen most of my experiences and learning outcomes in this blog, but if you have specific questions regarding any parts I did, I will be happy to help!

Section 6: Thanks

Special thanks to all the IMA fellows who gave me advices, helps and supports. Thanks Kevin who brought me 4 capacitors from electronic markets although I did put them into use (due to the constrain of time). Thanks Shawn, who came up with the idea of electromagnetic gun in the midterm and I stole it. Thanks Rudy, who supports me all the way in this class! Without all the helps, I couldn’t learn this much and finish this. Thanks to the show, I had the chance to display my work to others. I really didn’t expect that many people were interested in my work! Thanks for all the good words!

 

Lab report: Module Electronics (working with electrons) Kewei Xu

Lab Template: Modular Electronics

Introduction

In this lab, we supposed to get familiar with the reference sheet provided by manufactors of different electronics circuit. We would be looking at several sensors and actuators in this lab.

Experiment 1&2

I used the normal LED as my actuator in experiment 1&2. According to the reference sheet, the LED tolerate the voltage output of 2-3V and 1A. I chose to use this LED to indicate whether there were voice signal going into the microphone or not. I didn’t have the time to switch to a better actuator in this experiment. If I had enough time I would choose the RGB indicator as the actuator in my project.

Experiment 3&4

I used the microphone sensor in experiment 3&4 as my sensor. The sensor was module W104 and it has 4 connection pins: A0, G, + and D0. According to the reference sheet, the microphone should be connected to the Arduino with analog signals. The Vcc pin is connected with 5V DC power supply and the GND connection goes to ground of course. In this experiment, I used the analog pins as the output I would use in the following experiment.

Experiment 5&6

As discussed in the front, I used the microphone as the sensor and the LED as my indicator for whether there is signal going out from the sensor. The W104 sensor worked perfectly with its own functional light (embedded in the chip) blinked. However, the LED didn’t work very well. The LED did light up when there was sound, but the brightness was very low that is hardly noticeable. My guess is that it was due to the low voltage output of the chip.

BTW, I recorded the project from the other group since I found theirs were better. They were using the RGB light as the actuator and the distance sensor.

 

Pin Wiring to Arduino
A0 Analog pins
D0 Digital pins
GND GND
VCC 5V

Image result for arduino microphone

 

 

Lab Report: Creating a Timer Circuit (working with electrons) Kewei Xu

Lab Report: Creating a Timer Circuit

Introduction:

In this lab, we aimed to get a working understanding of digital circuits. We will use tools, techniques and instruments that help us to know whether a circuit is working and how to adjust it. The particular circuit we will be looking at in this lab is 555 time circuit, which is a regular circuit that the frequency can be adjusted by turning the circuit around it.

Material:

  1. 555 timer
  2. Resistors in different values
  3. Rheostat
  4. Capacitors in different values
  5. Speaker (or LED)
  6. Regulated power supply

Procedure:

  1. Schematic

    We started with wide search of what we could do with 555 timer circuit. Finally instead of using the schematic professor gave us in the lecture (with LED), Kevin and I decided to use speakers to do something different. We decided to use the schematic below as shown.
    Metronome Circuit
    http://www.555-timer-circuits.com/metronome.html

  2. Assemble a circuit

    We successfully assemble the circuit as shown in the picture above. However, due to the absent of some specific values of components, we used other components that have close values. We expected that there would be some differences, but should be big.
    The following is the video recording the performances of our circuit. As observed, the frequency of the speaker can be changed using the rheostat.

  3. Measure & check the datasheet

    After the circuit was successfully assembled and tested, Kevin and I did few measurement to see how much power we actually put on the speaker. Since we changed the schematic a little bit, we found that the speaker was not fully operating under its best state.

  4. Simulate the circuit in the computer

    I used the http://falstad.com/circuit/ to make a 555 timer circuit. In this simulation, I did a alternation of LEDs. Two LEDs are connected reversly, so one LED will turn on while the other one is off.

  5. Draw the circuit in Eagle

    After the circuit is successfully simulated in Falstad.com, I continued to finish the circuit drawing in Eagle. In Eagle, I used the sparkfun package to find all the components I want such as 555 timer, Vcc, resistors, capacitors, speaker and so on. The finalized circuit on Eagle was shown in the picture below:

  6. Draw a Printed Circuit Board

    Used one botton in Eagle it can convert the circuit to PCB easily. Only thing that requires more to do is rearranging the line. The picture below is the PCB board we had.

Conclusion:

It’s very easy for people to interprate the PCB as one of the hardest work on engineering career, even including myself. In my past 3 years of study in Electrical engineering, I never used or built one PCB on my own. However, the experiment we had today let me rethink about this problem. By using some softwares such as Eagle, we were able to do the circuit arrangement very easily. PCB is much smaller and much cleaner than the breadboard we used to have.

 

Harmful Radiation Research (Working with electrons) Kewei Xu

Is Cell Phone Radiation

—— Harmful radiation research

When I was still in primary school, my parents always used one argument to tell me not to play cell phones, which was cell phone would do harmful radiations to my eyes. I was terrified by them since I had no idea of what radiation was. “Radiation” sounds like something that could cut my eyes into pieces and make me blind. Plus I sometimes did feel tired after staring at the screens so I did believe my parents. 10 years later, when I have more times on my own and actually can choose to use phones and PC anytime I want, I decide to search for more infomations about this fact: whether cell phone will do harms to our eyes?

inna

 

Through many research, I found in this forbes passage, it introduced a very comprehensive analysis of what radiation is harmful for human. The word ‘radiation’ sounds scary, but in reality it includes any type of electromagnetic wave (and some particles too, but let’s not get into that here)—gamma rays, x-rays, ultraviolet light, visible light, infrared light, terahertz, gigahertz, megahertz, microwave, and radio waves (see:Electromagnetic spectrum).

The electromagnetic spectrum is broken up into two parts based on whether small doses of that radiation can cause harm: ionizing radiation and non-ionizing radiation. Ionizing radiation—UV, x-rays, and gamma rays—has enough energy in one photon (quantized minimum packet of light) to remove electrons from atoms or break apart chemical bonds. It is because of this potential for cancer-causing DNA damage that you wear a lead vest when you get x-rays at the dentist and you are advised to wear sunblock when you go out in the sun. One can’t avoid natural (radon, cosmic rays when you are up in an airplane) and man made (diagnostic x-rays) sources of ionizing radiation completely, but it is reasonable advice to minimize exposure when possible.

Then there is non-ionizing radiation, which encompasses the vast majority of light we are exposed to: visible light from lightbulbs, infrared light from an oven and from people, gigahertz light from our wifi, megahertz light to/from our cell phones, and radio waves hitting our car radio. They are not harmful in small doses because one photon does not have enough energy to ionize atoms and/or break apart molecules. In very large doses, non-ionizing radiation can be harmful.

To know whether phone is harmful to human, there are 3 questions to ask:

  • What frequency do they emit/receive and what is the power of this radiation?
  • How does this frequency interact with matter?
  • Is cell phone radiation enough to cause damage to humans, given its frequency, power, and interaction mechanism?

This passage gave me several conclusions:

  1. The radiation from your cell phone is NOT harmful to human at all.
  2. The fact that people who spend to much time staring at screens have higher chance to get short-sighted and put on glasses than normal people is true.
  3. The reason of this fact is actually centered at the “time” you spend on screen, not the screen itself.

 

Midterm: Light Tunnel (Working with electrons) Kewei Xu

Light Tunnel

—— Working with Electrons

Introduction

When Leyden Jar was first invented, human never thought about there is a moment in the near future that electricity is the most important power which motivates our world. All the small electrons moving in copper coil is our most reliable helper in our work and life. How electricity is generated from other energy is very important but only a few people understand. The idea of this project was drown from one time that I went through the undersea tunnel of Huangpu river in Shanghai. I saw the LED go through my head one by one and I imagine I was a small magnet that is going through a hole, and the lights around me turned on one by one as I go through them. I came up with the idea that I can reproduce this scene with very simple materials in our life. This project is aimed to give audiences a very direct feeling that how electricity is generated in our life.

Outline

I would say this part is a small introduction of math and physics knowledge, rather than an outline. This is indispensable in any report that is related to any physical reaction to run away from some maths.

In this project, one and maybe the only one equation is Faraday’s law of electromagnetic induction, which says that the magnitude of electric magnetic force induced is directly proportional to the number of turns in a coil and the rate of magnetic flux changes. In order to generate EMF that is suficient for lighting up LED, I need as many turns in the coil as I can, and change magnetic flux as fast as I can. To do the second one I have two options: 1. moving the magnet quickly. 2. using a strong magnet. 

Materials

  1. 8 coils (240 turns)
  2. Low power LED (2V 0.5A)
  3. A strong magnet

Just as simple as these.

Procedure

Firstly, before everything start, I needed to verify my thought with the materials that I have in the lab. I used a copper coil and a LED to verify Faraday’s law of electromagnetic induction. The following is a video that records how I did my experiment. I used ocilliscope to record the peak of the voltage I can induce. As you can see, the peak that I induce is about 2V and the LED successfully turned on at that moment. This also gives me confidence that I can finish my project. A good begining is half of the success, isn’t it?

Video: Trial with simple equipments

Secondly, after everything I ordered arrived, I started to build my project. Of course, this started with build one and gave it a try. Unfortunately, I didn’t record this trial. Furtherly, because I needed to connect all eight coils in one line in order to make sure one move of magnets can go through all the coils, I put all 8 coils on a pair of chopsticks. As shown in the video below, everything has been proven working correctly except the magnet sometimes will bounce into the coils. After I did a closer look at the device, I noticed that the chopstick is not straight. This mistake could be avoided if I detected this problem earlier.

Video: Failure with chopsticks

Then everything else became clear: I need to change to holding structure to a relatively straight and flat one. With the help of Karen, I chose to use a plastic board. So I redid everything before this on the new board.

Using this new design, I did two records of success in two different situations: with lights and without lights. The light situation is to record the movement of the magnet through the coils, and the without lights situation is to augment the lighting effect. Let’s take a look at my two records under slow motions.

Video: Success with light.

Video: Success without light

Small notes: It’s obvious in the dark situation that light is turn on one after another. Also, the reason why red lights turn on first then follow the yellow lights. This is due to the connection of two LEDs. Since LED is diodes, so by connecting them inversely, we can make them turn on one color at one directions.

Untill now, everything I wanted to achieve and everything that I can verify at the begining are done. The difference between my ideas and the reality is due to my overestimation of the magnetic force of magnetic balls, it directly results in my project cannot have more flexibility.

Conclusion

In this project, I successfully verified the Faraday’s Law of induction by using several simple devices. My inspiration was drawn from the undersea tunnel of Huangpu river. However, I do realize there are still many places that I didn’t do well in this project and many future development that I can do.

  1. A coil with larger inner radius and more turns will be better suitable for my project. Larger inner radius will enable more moving space for magnets, so will reduce the risk of bouncing. More turns will let the induction be easier. The one I used was 240 turns and it costs approximately 2 kuai and I saw that there is a 480 turns which costs 5 kuai.
  2. I should choose a better magnet material. The one I use for presentation was not very suitable for the initial idea I had, that the magnet should go through the coil very easily and the magnet should be small. There might be a more suitable magnet out there in the market.
  3. As suggested in the presentation by an IMA follow, I could make a supportive machine that will automately move the magnet instead of releasing it everytime by my own hands. This suggestion was very valid since this will make the device more controlable and manageable.

As you can see, my midterm project was far from being perfect. However, I did feel that I somehow express my idea and my understanding of electrons in our lifes successfully. Just like what I joke about myself, “my project is the only project in the classroom that do not require a power supply”, I was delighted that I can see something being created from nothing.

Midterm proposal (working with electrons) Kewei Xu

Midterm project proposal

1. Project Title: Light Tunnel

Image result for light tunnel

Just like the picture below shows, my project is similar to a Light tunnel. When an object passes through the tunnel, the light will turn on following the path of object.

2. Project Statement of Purpose

In our daily life, electromagnetism is widely used everywhere. Generating electricity, motor, communication, wireless and so many other aspects are using the knowledge of electromagnetism. Thanks to Faraday, Maxwell and other scientists, we found this amazing relationship between electrons and magnetism. In this project, I tend to utilize this relationship and make some interations between them. This project incorperate the knowledge of generating electricity from changing magnetic field with some art elements, which I believe is the essential idea of IMA and this course.

3. PROJECT DESCRIPTION

There are several materials I need for this project.
1. Coils with enough turns
2. Magnets (as strong as possible)
3. Low Power LED light (Lower the power it needs the better)

According to Faraday’s law of electromagnetic induction, any changing magnetic field will induce some electric voltage difference in a close loop. From the equations shown below, the magnitude of the induced voltage is directly propotional to number of turns of the coils and how fast the magentic field changes. This is also related to the materials I required.Theoretically, I will use one coil, which performs as a battery, and one LED combination to be one unit of my project. By introducing a changing of magnetic field around the coil, which is done by passing a magnet through the hole of the coil, there will be induced voltage across two terminals of the coil. Therefore, the LED can be turned on. If one single unit of my project is working, I will connect several of them cascadely and create a “light tunnel”. Whenever a object (which is a magnet) passes through the tunnel, the LED will follow the path of the object turn on/off.

The purpose of this project is to use some scientific knowledge we learnt in class, recreate and test that theory in cooperating with some art elements. Hopefully everything will goes well as I implement everything physically.

I finished a small experiment on Tuesday which works out well using the coil we had in class and a 2V LED. Yeah!

 

 

 

Kinematic Sculpture (Working with electrons) Kewei Xu

Kinematic Sculpture —— Building a magnetic pendulum

The idea of my kinematic sculpture is coming from a pendulum. In a no-friction world, a pendulum will keep moving forever in a constant frequency. Due to this characteristic, the pendulum is widely used in time recording in ancient time (figure 1,2 &3). In my kinematic sculpture, I tended to use one magnet as the pendulum and hung it over in the air. I put another moveable magnet right under the hanging magnet without touching it.

Image result for clock pendulum

Figure 1 Clock pendulum 1Image result for clock pendulum

Figure 2 Clock pendulum 2

Image result for clock pendulum

Figure 3 Clock pendulum 3

My intuition is to give the pendulum an initial force, which makes the pendulum start to swing. At the time it swings close to the underlying magnet, due to the counterforce or attracting force, the underlying magnet will have some movements. And I cautiously set the distance between two magnets, which will enable the force to be not too small, but also ensure they will get contect physically. The following video is recorded in 2 minutes duration, but I only uploaded the first 40 seconds to see the actual result.

The original setting was hanging the string on a metal stick instead of hands in the video, but I made this change in order to have a little control over the whole device. As we can see, when the pendulum passes by the free magnet, the free magnet is moving randomly.

My interpretation of kenematic sculpture is something that doesn’t require the outside forces, or just need some nature outside forces such as wind. Another point I want to illustrate in my kinematic sculpture is that the movement can be completely random or following some patterns. Since many objects follow no law of movement in our world, for example the movement of the electrons. This random is a way of beauty and many artists actually use this unpredictable movement to create many amazing works. On the contrary, some other objects follow some laws, just like the pendulum. This represents how we human interperate the world. We always try to analyze the world and try to find some inside connections, and it works very well in many science problems. This movement can still be a way that we could produce kinematic sculpture.

Lab 5 Ampere Law & Electromagnets (working with electrons) Kewei

Lab 5 Ampere Law & Electromagnets

Introduction

In this lab, we were going to use the simulation tool, which is a website www.falstad.com, to simulate some circuits and then try to build it with the same component.

Experiment 1Simulation of a charging capacitor

In experiment 1, the RC circuit is built. By switching on the switch at t=0 time, the capacitor starts to charge up. We could see the exponential curve of the voltage across the capacitor and it stablize around 10V, which is as same to the voltage supply. Also, we also observe the exponential decrease of current in this case.

Figure 1 simulation of RC circuit

https://www.falstad.com/circuit/circuitjs.html?cct=$+1+0.5+0.5999443210467817+53+5+43%0Ar+176+80+384+80+0+1000%0As+384+80+448+80+0+0+false%0Aw+448+80+448+352+0%0Ac+448+352+176+352+0+0.0047+9.999999478807508%0Av+176+352+176+80+0+0+40+10+0+0+0.5%0Ao+3+1+0+4099+10+0.0125+0+2+3+3%0Ao+0+1+0+4099+10+0.0125+1+2+0+3%0A38+3+0+0.000001+0.000101+Capacitance%0A38+0+0+1+101+Resistance%0A

Experiment 2Measuring a charging capacitor

To charge the 4.7mF capacitor (we use 220 ohm resistor), theoretically TAO would be TAO=RC=220*4.7m=1.034s. To be fully charged, we need 5 TAO, which will be 5*1.034s = 5.17s. In the following record, the scaler is 1s/block, so it’s 5s in total. Theory matches with experiment! yeah!!!!!

Figure 2 Charging the capacitor in real life

Experiment 3Adding loops

Figure 3 simulation of RL circuit

In experiment 3, the RL circuit is built. By switching on the switch at t=0 time, the voltage across the inducor starts at a very high place and decay exponentially. Consequentially, the voltage across resistor starts to increases exponentially. This can be explained easily using Lens Law, which says that inductor doesn’t allow the current to increase sharply.

Experiment 6 Make a solenoid

In experiment 6, a simple solenoid is made using wires and a power supply (this was done by Kevin and Shawn). By closing the switch or connecting the circuit, the inductor will become a big magnet and push out the coil. This function makes the device similar to a “gun”.

Figure 4 the solenoid made by Shawn and Kevin

Conclusion

In this lab, we took many inside experiment with the transient circuits, which includes RC circuit, RL circuit and solenoid. We did them both on simulations based on computer software and physical component, which is very helpful for us to get understand of the behavior of transient circuit.

Lab 4 report (Working with electrons) Kewei Xu

LAB REPORT—-INDIRECT MEASUREMENTS

Objective:

This experiment is aimed at how we can measure and analysis circuit element without directly measure the components.

Materials:

  • Regulated Power Source
  • Voltage Meter
  • Current Meter
  • Wire
  • LED
  • CR2032 Battery
  • 1k ohm resistor
  • 220 ohm resistor

Procedure:

Experiment 1: Calculating resistance of a wire

By connecting the current meter and wire in series with a low voltage power supply, adjust the voltage level until the current in the current meter is 1mA/1A/2A and calculate the resistance of the wire.

Experiment 2: Measuring internal resistance

We use two batteries together with the output of roughly 2.4V. Use the wire to connect the ends of an LED to the ends of the battery. Pay attention to which prong is positive and which is negative on the LED. With all the readings, we will be able to calculate the internal resistance of the LED.

Experiment 3: Measure power

We use a 1k and 220 ohm resistor and set up a circuit that consumes 1 watt.

Experiment 4: Resistor divider (Run out of time)

Observations:

Experiment 1:

In this experiment, due to the small resistance of the wire, we could induce 1mA in the circuit steadily.  With 0.11V power supply, the current was 1.16A. With 0.25V power supply, the current was 2.00A.

Experiment 2:

With a red LED, we used two 1.5V batteries which, in total, emit 2.37V as they were not fully charged. The choice of 2 battery was because one battery cannot power up the LED itself. The current reading was 72.5mA.

Experiment 3:

Using a 220 ohm resistor, supplying 14V from the power supply.

Results / Conclusions:

For all the experiement, the schematic is shown in the figure below:

Experiement 1:

By the definition of Ohm’s law, R=V/I, the resistance of the wire can be calculated as 0.1ohm=0.11V/1.16A and 0.125ohm=0.25V/2A.

Experiment 2:

We used two batteries to power a red LED. We noticed that the current started increasing as the resistance started decreasing which shows the relationship between the two values. This indicates that the resistance of the LED will change as the temperature is heating up. The internal resistance of the LED can be calculated as 31.6ohm=2.37V/0.075A when it’s at a steady state.

Experiment 3:

For this experiment, we used 220ohm resistor to produce 1W power. With 14V at  the power supply, the power is at 0.89W=14^2V/220ohm.

Conclusion:

These experiments helps us to get familiar with some physical notations such as resistance, power and current. We come to recognize that there are multiple ways to measure some parameters which we can hardly measure directly in our circuit. This would be very useful in the further study of circuit.

Working with electrons: Generating and using electricity (Kewei Xu)

Lab Report

Introduction

The goal of this lab was to get familiar with instruments and toos to measure and using magnetic field.

Description

There are total four experiments done in the lab.

  1. Using electricity —- get a sense of how much voltage and current is affordable for LED and motor etc.
  2. Making a battery —- using the knowledge for chemistry, building up a battery and do some necessary measurment.
  3. Making a motor —- using the knowledge of electromagnetism to create a motor.
  4. Stepping down and stepping up —- try to step down and step up voltages using transformers.

Data and procedure

  1. In experiment 1, we connected a LED or a motor to a 5V voltage source.
    1. The LED breaks when approximately 8V cross it and 2A current pass through it.
    2. The motor didn’t break in our experiment. We increased the voltage up to about 30V and the current was about 5A, however, the motor still run. But we did see smoke coming out and sparks inside the motor, which indicates that this voltage is no longer its normal operating voltage. Due to limitation of our power supply and the safety concern, we didn’t find the threshold voltage for motor. The video below records the process.
  2. In experiment 2, we successfully create a battery using two oranges. By placing copper and zink strips into the orange and using them as the postive and negative pole of the battery, we were able to detect some voltage across two terminals. The picture below shows how we connected the battery and how we power up a watch.

  3. In experiment 3, we recreated a motor like we did in lab 2. The following video records the setup and the motion.

  4. In experiment 4, we experienced the step down and step up devices using transformer. We successfully created a spark producer after step up devices. The following is the picture for sparking device.

Conclusion

This lab gives us a opportunity to experience how electricity is created and how electricity is used to power up devices. This is truly important for any engineers who wish to work with electrons to understand the inside logic of electricity in order to fully make use of it. By know these knowledge, it’s also helpful for us to avoid any innecessary danger while we are dealling with high voltage devices and using transformers etc.