From the Blog Manager

Dear readers,

It has certainly been a while since I updated a new science experiment.

I came back to Woodbury, Minnesota for my senior year in highschool.

Ever since I came back to the United States, I have not been able to care for my blog for a while because of school work, extracurricular activies, and college applications.

To concentrate more on school and college applications, I have decided to take a break on running the blog.

I will actively update more experiments and articles after I enter College.

I am terribly sorry for notifying you readers about the delay with such a late notice.

Thank you so much for giving care and support.

I will return as soon as possible with more interesting and fun homemade experiments.

Thank you

Predicting the Working Temperature of the Light Bulb's Filament

What is the temperature of light bulb?
(by Daniel Lee and Shin Lee)

There is a relationship between the resistance of the material and its temperature.
We call this Temperature-resistance relation of the material.
For metal, the resistance increases when its temperature rises.
It can be indicated as follows;

R=R0(1+αT)

It says if we know the resistance, we can calculate the temperature of the wire.
Similarly, if we know the (temperature of the wire), we can calculate the (resistence) of the material.

Alpha=temperature resistance coefficient
0.0039 for most metal

1)What is the room resistance of the bulb (4.2)ohm
2)What is the room temperature? (25)oC
3)Then, what is the Ro from the above equation? (4.057 )

Turn on the cold small lightbulb using the batteries and aligator clips for about a couple of minutes.
Then read the current using the DMM(Digital Multi-Meter) as shown below:

From the previous lab journal, The DMM(Digital Multi-Meter) is a Stethoscope for Electric Circuit, we can get the values below.

1)resistance of the hot bulb? (108.47ohm)
2)the temperature of the hot bulb?
108.47=4.057(1+0.0039T)
0.0039T=108.47-4.057=104.413
Therefore, T=104.413/0.0039=26772.5641 Degrees Celcius=27045 Kelvin.

It is well known that the sun's temperature is 5777 Kelvin.
The sun, obviously, is the hottest thing that exists in our solar system.

Is this calculation right?

Reading Resistance with Color Codes.

Tools: Digital Multi-Meter, Registers with Color Code.

Measuring Resistance

How to read the resistance from the DMM.

If you wish to measure the registance accurately, make sure to hold the register tightly with the probe.

How to read the resistence by the color code on the surface of registers.

Colors' Values
Brown 1
Red 2
Orange 3
Yellow 4
Green 5
Blue 6
Purple 7
Gray 8
White 9
Black 0
Gold 5% error
Silver 10% error

For example:

A register that has color codes of brown, black, red, gold can be measured as follows:

1) (brown, black, red, gold)=102(5%)=10*102(5%)=1000 ohm
(5%) error indicates that the resistance is greater than 950ohm but less than 1050ohm.

Second Example which was shown in the photo above can be calculated through:

(orange, orange, brown, gold)=330(5%)=33*101(5%)=330 ohm
(5%) error indicates that the resistance is greater than 313.5ohm but less than 346.5ohm.

The value from the DMM, 333.7ohm, satisfies the range shown above on the 2nd example.

The DMM (Digital Multi-Meter) is a Stethoscope for Electric Circuit.

Caution: Be careful for the safety! Electricity is very dangerous and very hot sometimes, so you may burn your finger!

Tools: Digital Multi-Meter, Battery, Battery Holder, Socket, Light Bulb, Aligator Clip, LED

It can be used in different ways.

Here are typical examples of how to use DMM.

(1) Measuring dc voltage

I made two 3.2V DC with four 1.6V DC battery with two holders.
I only thought that batteries were only 1.5V. However, when measured, the instrument shows 1.6V.
The series connection of the two 1.6V batteries creates 3.2V.

(2) Measuring ac voltage

AC indoor power line in Korea has 225.3V
Koreans normally call the power line’s voltage 220V. However, it is actually 5.3V higher.
Compared to the American power line, Korean power line is more lethal.

(3) Measuring dc current

The indicator shows that the current flowing through the small light bulb is 29.5mA.
The supplying voltage is 3.2V.
The (working) resistance can be calculated with Ohm’s law.
V=iR.; 3.2V=29.5mA*R
R=3.2V/29.5mA=3.2V/0.0295A=108.47
The room resistance was 4.2ohm at 25oC.

(4) Measuring temperature

Digital Multi-Meter can be also used as a Thermometer.
I positioned the temperature probe between my armpits.
It says that my body temperature is 37oC.
There could have been an error because a cloth blocking my body and the probe.

My profile

It seems that I have not introduced myself fully.

I am currently a foreign student who is studying in Minnesota in New Life Academy.

I had many influence in science from my father who is a Professor in Mechanical Engineering.

After I learned interesting concepts of physics and basic scientific knowledge, I decided to share several of experiences on a blog.

I wanted to create a blog that anyone could use and perform.

Therefore, I mainly did experiments that can be done with typical things that can be found at home.

I sure hope that people would be able to step closer to the world of science!

P.S. After reading the reports that I have uploaded, you might have a confusion because of complicated physics theory or my english.

You can ask questions or parts needing clarification to my e-mail.

My email is chungjae12@yahoo.com

I will respond to your e-mail ASAP.

What is the difference between the heat transfer in the air and in the water?

I am terribly sorry for the late update.

It was my father's birthday.
We went the Baskin' Robbins 31 to order a bucket of ice cream.
Inside the bag, we found some solid carbon dioxide.
Such material sparked our curiosity.
We began our experiment right away.
Tools: Solid Carbon Dioxide, Cup, Water, Spoon

Procedure:
1. Get a cup of water and a spoon.
2. Add a block of solid carbon dioxide into the water.
3. Observe the evaporation.

Discussion:
What is the difference between the sublimation with water and the sublimation with air?
The sublimation in the water is very vigorous or strong compared to the sublimation in the air.
The sublimation in the air can be regarded as a heat transfer from the solid to gas.
However, the evaporation in the water can be regarded as a heat transfer from the solid to liquid.

The molecular density of in the air is less dense than that of the molecular density in the water. Here, the molecules can be regarded as a media for heat transfer.

I heard that the above heat transfer called as a convection heat transfer among 3 modes of heat transfer, conduction, convection and radiation.

Can you imagine yourself in a public bathtub?
If you see the thermometer in the Sauna room, it would be 80 deg Celsius or 170F.
However, you can endure the heat of the water.
This time, imagine yourself in a tub of water with temperature of 80 deg Celsius or 170F, (This condition is really dangerous, really dangerous so that you may be killed or hurt. It is really dangerous)

What is the difference between the two phenomena above?
The first one is similar with the situation the dry ice in the air and the second one is similar with the dry ice in the water.

Extra Experiment:
Can you make Sprite at home?

Tools: Previous Mixture, Sugar

Procedure:
1. Add a proper amount of sugar to the previously created mixture of solid carbon dioxide with water. 2. Take a little sip to the chemical. (The origin and the usage of the solid carbon dioxide was unknown. There are possibilities of it being poisonous.)

It did not taste as good as commercial Sprite at Wal-mart!

Acceleration of the Elevator Box

People tend to call me overweight.

To change the stereotype, I decided to change my weight in a short time.

Realizing that healthy diet and daily excercise takes several month, I searched for quicker way of changing my weight.

Tools: Bodyweight Scale, Elevator

Introduction:

Weight in scientifical definition is a force exerted on an object by gravity.

I decided to see the variation of weight through difference in gravity.

Procedure:

1. Find a nearby elevator.

2. Go to the highest level.

3. Go on the bodyweight scale and measure the actual weight.

4. As the elevator goes down, observe the change of weight.

Observation:

My weight is 80kg. (80kg-g is more correct or accurate expression instead of 80kg. 80kg is the mass of my body, however 80kg-g is the weight of my body, that is the force that the gravity makes.)

When the eleator went down it pointed at 75kg.

When I pushed the first floor button at the twentieth floor, the scale indicated at 75kg for the first three floors.

The reason for the sequence is stabilization.

During the first three floors, acceleration of the elevator occured from zero to 5m/s.

However, after the first three floors, the elevator moved at a constant speed at 5m/s.

(Constant velocity means no acceleration or addition of force. However, acceleration indicates that there was an additional force affecting our body.)

Conclusion:

We can apply the Newton's Second Law to this experiment.

Summation of the external forces is equivalent to inertia force: F=ma.

(g=gravity, a=acceleration, 75g=measured value of weight during down of elevator, 80g=weight of my body at initial state, 80a=inertia force of my body)

75g-80g=80a

-5g=80a

therefore, a=-0.613m/s^2

a is the acceleration of the elevator.

Proving Bernoulli's Equation at Home(2)

Tools: Hairdryer, Stool, Sheet of Paper, Tape


Introduction:
As mentioned in the previous experiment, Bernoulli's Equation is used to predict real fluids such as air.
I performed one more experiments to help the reader fully understand the concept of Bernoulli's Equation.

Experiment 1: Hairdryer and a Sheep of Paper
Procedure:
1. Attach a sheet of paper on a stool.

2. Turn the hairdryer on and put it above the stool pointing the paper.

3. Observe the temporary stable position of the paper.

Discussion: According to the last experiment, Bernoulli's equation told us that when the velocity increases, pressure decreases.
Before using the hairdryer, the paper was bended downward due to gravity.
By blowing the air paralel to the seat of the stool, the sheet of paper moved upward.
This sequence indicates that the wind worked as a resisting force of gravity.
On step 3, the paper was fixed at a specific position, which indicates the balance of force between the wind and gravity.
The upward force which lifted the paper was cuased by the pressure difference between the two different sides of the sheet of paper.
Furthermore, the presure difference was caused by the flow of the fluid.
Since there was a flow from the hairdryer on the upper side of the paper, there was no flow under the sheet of paper.

Proving Bernoulli's Equation at Home(1)

Tools: Ping-pong ball, Hairdryer, Paper, Tape

Introduction:
Bernoulli’s equation describes the flow of ideal fluid.
This innovative equation helps us to predict the motion of real fluids such as air and water.
It is well known that when velocity of the fluid increases, pressure decreases to keep the balance in any part of the fluid.
We can prove the equation by the following two experiments by using only simple home materials.

Experiment 1: Hairdryer and Ping-pong Ball
Procedure:
1. Place a ping-pong ball on top of a hairdryer.

2. Turn the hairdryer on with the ping-pong ball at the top and observe.


Observation:
When the air was not coming out, it was difficult to balance the ball on the top of the hairdryer. Although the ball had variation in its positions, the ball did not fall from the top when the cool air blew out from the hairdryer. The ball was being balanced by the air.

Discussion:
The phenomenal can be explained through the delineation below.



The equation above is the Bernoulli’s equation.
It shows that when the velocity increases, pressure decreases, and vice versa.
On the depiction, vertical arrows indicate the velocity magnitude.
Horizontal arrows depict the magnitude of the pressure.
The picture on the left shows the ball’s instantaneously unstable position on the left side of the hairdryer.
The velocity on the right side of the ball instantly increases when the ball is on the left side of top of the hairdryer.
Consequently, the pressure on the left side increases which pushes the ball to the center or the right direction.
The same sequence occurs on the right side.
In conclusion, due to the restoring force to the ball, the ball can maintain its position around the center of the exit of the dryer.

I give thanks and partial credit to my father who advised me and helped me with the experiments.

Gravity and Zero Gravity

I am so glad that this blogspot is going better than I first imagined.

I hope this blog hopefully affects and answers the curiosities of other fellow student scientists.
To celebrate this occasion, for the first experiment, I decided to test about the thing that always affect us: Gravity.

Tools: Empty bottle, Needle, Water.

Introduction:

What is the difference between gravity and zero gravity.

The difference can be found from whether we can feel it or not.

Frankly, there is no such thing as zero gravity because gravity is everywhere.

The term zero gravity got its name because it is nearly impossible for us to feel or even see the existence of zero gravity.
Using three simple tools above, we can see the existence of no gravity.

Procedures:

1. Put a hole on an empty bottle.

2. Fill the bottle with water.

3. Check the water flow from the hole.

4. Drop the water bottle and observe the stoppage of water flow.

Observation:
The water flowed while holding. However, the flow stopped when the water expirienced a free fall.

Discussion:
The reason why water flowed from the bottle is because force uplifting the water from the bottom of the bottle and the gravity squeezed the water to flow out of the hole.
The water stopped flowing from the bottle because the force uplifting the water turned downward by the free fall.
Therefore, the water instantly experienced the state of being in zero gravity.

The First Step

To celebrate the opening of this blog, I decided to put an article.
Every project has an initiative step.
First step for experimenting is learning what can be used for scientific experiments around us. Therefore, I spent about thirty minutes to see what could be used for experiments.

I never realized how many things in our normal day live's tools can contribute to scientiifc experiments.
Since majority of my experiments are related to Physics, I decided to use use couple of rulers, tape, pliers for cutting and holding substances, and a weight meter.
I am pretty sure there are way more things that can be used for experiments around us.
But for now, these should be enough.

Introduction

I was never interested in Science before. Every time I heard the word "Science", I would cover my ears on the spot. However, ever since I chose my future major as Engineering and started giving small interests in science, I was fascinated by the deep logic within every concept of science. Having an erge to share my joy of learning science, I decided to record my progress and experiments on blogspot. I hope you enjoy reading my experiment journals.