Blog 7. Building motors in class.

Mr. Chung gave us the opportunity to build a motor in class today with a friend.
My partner was Daniel, and we had many challenges during the experiment of building a working motor.


During the period, we only had the first 30 minutes of class to hammer since it was a very noisy distraction to other classes... (HAMMER TIME!)
We hammered four 4-inch nails, 2 cms by 3 cms in length and width on the wood.
I started sanding the brushes (sides of the pop can) with sandpaper, which didn't seem to be one of the very old generation ones.

We then stuck the stick through the cork, along with two nails parallel beside the stick.

Next, the coiling got confusing... instead of coiling parallel (the PROPER way), I coiled it perpendicular to the nails = the WRONG way.
With some tape to secure the properly coiled cork (much later after many tries), we decided to go for round 1 of testing.

Round 1 resulted in a fail. This was because our brushes may not have been sanded enough. One of the nails in the cork did not touch the brush.

Round 2 resulted in... another fail. (QQ) Our paper clips were not stable enough and we ran outta time to fix it...

More updates will be posted tomorrow! Maybe.

Blog 6.1 Note: Electromagnets & Right hand rules

*NOTE: these apply to CONVENTIONAL CURRENTS only.

Oersted's Principle - a circular magnetic field is produced when charge flows through the conductor

Right hand rule #1 (conductors):

• The thumb for RHR1 points in the direction of the current flow, from positive (+)
  
  
• The CAT'S CLAW (meow~!) = the direction of magnetic field around the conductor
  
  

Right hand rule #2 (coiled conductors):

• The thumb for RHR2 points to North
  
  
• The CAT'S CLAW (meow~!) = the direction of magnetic field around the conductor

The dot and the X (RHR1)

To look at the conductor in another way, we represent the dot as in the page, and the x as out the page.

electromagnet - the strength of the magnetic field (represented by B)

Blog 6.0 Note: Introduction to Magnetism

Picture: Visible magnetic fields from the help of iron filings

magnetic field - a physical field produced by a magnetic object

North/South - labels for two different magnetic characteristics that create the magnetic forces.

The law of magnetic forces:

• Opposites attract

• Similar repel

test compass - helps find a magnetic field (sorta like test charge in electrostatics)

ferromagnetic metals - a metal with different elements mixed together (e.g. iron, nickel, and cobalt). Has an atomic structure which makes them strongly magnetic.

domain theory of magnets - 'smaller magnets' that make up magnetic objects

Picture: The direction of the dipoles are based on being magnetized by another magnet

Domain theory - all large magnets are made up of small, rotatable magnets = dipoles
if the dipoles line up, then a small magnetic domain is produced.






LOLWAT: the North pole is actually 'south', since the North points in the direction of the North pole.

Blog 5.1 Note: Kirchhoff's laws.

• KIRCHHOFF'S CURRENT LAW:
  
  total amt of current into a junction pt. of a circuit
  =
  total current that flows out that same junction
  
  
  

• KIRCHHOFF'S VOLTAGE LAW:
  
  total of all electric potential ↓ in a current
  =
  any potential ↑ in that circuit loop.

... similar to conservation of electric charge/energy: no gain or loss in energy.

Blog 5. Note: Resistance - Ohm's Law.

flow in a circuit depends on two things (characteristics):

• the amount of push
  

• the nature of the pathway

RESISTANCE: the opposition to flow.
The more difficult the path, the more opposition to the flow.

R = V/I, a ratio called 'Ohm's law'

R --> volts per ampere = Ohm
V --> volts
I --> current --> Amperes

The resistance of a conductor depends on:

• length
• cross-sectional area (thickness)
• material its made of
• temperature

Factor	Description	Proportionality
Length	The longer the conductor, the greater the resistance.	If length is doubled, resistance is doubled. R1 / R2 = L1 / L2
Cross-sectional area (thickness)	The thicker the conductor, the less the resistance.	If thickness is doubled, resistance is ½ original. R1 / R2 = A1 / A2
Type of Material	The general measure of resistance of a substance = Resistivity (unit: Ω · m)	If resistivity (p) is doubled, resistance is doubled. R1 / R2 = P1 / P2
Temperature	Greater molecular motion @ higher temperatures tend to ↑ resistance.	↑ in temp. of the conductor usually ↑ in the resistance, but not for all substances.

SUPERCONDUCTIVITY - ability of a material to conduct energy w/o heat loss due to electrical resistance.

Blog 4.1: Fun stuffs~

http://phet.colorado.edu/en/simulation/circuit-construction-kit-ac-virtual-lab

I found this online and thought it would be helpful for other visual learners (like me), and being able to experiment with AC/DCs.

Have fun~! :D

P.S. There are other science topics, such as Biology and Chemistry to try out!
P.P.S. The program requires Java.

Blog 4. Prelab: Using Voltmeter and Ammeter

Name	Symbol	Unit	Definition
Voltage	V	Volt	Potential energy per Coulomb of charge between two points. V = E/Q
Current	I	Ampere (A)	The rate of charge flow I = Q/t
Resistance	R	Ohm (Ω)	The measure of difficulty of the flow in an electrical current. R = V/I
Power	P	Watt (W)	The rate of energy passed on to different loads within a circuit. P = I · V

Blog 3.1 Note: Diagrams of different circuits

SIMPLE CIRCUIT

A simple circuit is made of a cell (i.e. battery), and a load.

OPENED CIRCUIT

An opened circuit is composed of a cell (i.e. battery), a resistor, and an opened switch.




SHORT CIRCUIT

A short circuit is composed only of a cell (i.e. battery) and no resistor.
This is a dangerous type of circuit.
(Please do not try this at home!)



SIMPLE SERIES CIRCUIT

A series circuit is composed of a cell (i.e. battery), and loads connected one after another in one path.




PARALLEL CIRCUIT

A parallel circuit is composed of a cell (i.e. battery), and loads that are connected parallel to each other, with more than 1 path. This kind of a circuit can be used with a switch to keep only one of the light bulbs on.

Blog 3: Energy balls; the expensive pingpong version.

Cozy energy ball~

Q1: Can you make the energy ball work? What do you think makes the ball flash and hum?

Yes, I can make the energy ball work.
To make the ball flash and hum, a complete circuit must be made. We are able to conduct some electricity so by putting your fingers on both parts of the metal, it completes the circuit.

Q2: Why do you have to touch both metal contacts to make the ball work?

One must touch both metal contacts to make the ball work to have a complete path for the positive charge flow to move to the negative terminal.

Q3: Will the ball light up if you connect the contacts with any other material?

This depends on the conductibility of the material. If the object is made of metal (i.e. fork), then it is a able to light the ball up because it is a good conductor. Bad conductors, such as a desk, is a bad conductor and cannot make the ball light up.

Q4: Which material will make the energy ball work? Test your hypothesis.

Our group assumed that metallic objects would make the energy ball work because they are good conductors of electricity. Our hypothesis was right; the metal ring of a binder was able to make the energy ball work.

Q5: This ball does not work on certain individuals, what could cause this to happen?

Dry skin -- since the current flows out from the positive terminal (one finger) to the negative terminal (other finger), the person will be able to complete the circuit if he/she has enough moisture. This is because the salt content and other impurities in our bodies and fingers are able to conduct electricity, so having dry skin (not enough moisture/impurities) causes the person to be less of a good conductor.

Q6: Can you make the energy ball work with all 5-6 individuals in your group? Will it work with your class?

Yes, I can make the energy ball work with all the members in the group.
It will work with the entire class, as long as the circuit is complete (we're all touching pinkies).

Q7: What kind of circuit can you form with one energy ball?

A simple circuit can be formed with one energy ball.

Q8: Given two balls (two groups): Can you create a circuit where both lights up?

Yes, by adding another ball into the simple circuit, you have just created a simple series circuit!

Q9: What do you think will happen if one person lets go of the other person's hand?

If one person lets go of the other person's hand, then both energy balls will not light up/hum. This is because a circuit is a complete path, so if one person lets go, the balls will not light up/hum.

Q10: Does it matter who lets go?

No, this is because in a series circuit, it is still only made up of one path, so whoever lets go will still disconnect the circuit.

Q11: Can you create a circuit where only one ball lights up?

Yes, and this circuit is called a parallel circuit.

Q12: What is the minimum number of people required to complete this?

One person minimum is required to complete this. The person can hold one energy ball in one hand, and the other in the other hand, and the finger is the switch. In each hand, the circuit is complete by using 2 fingers; one for each metal strip. The switch can be turned 'off' by lifting the finger off of one circuit, therefore having only one energy ball flashing/humming.

Blog 2. About yesterday's Structure Challenge.

Image: Si Yuan trying to make our structure stand... haha.

Yesterday, Mr. Chung randomly popped a structure challenge to the class.

We were assigned groups and told to plan a tall, but stable structure (aesthetics came last).

In group 2, we decided to go with a triangular base made up with 2 pages of newspaper.

Unfortunately, we did not know that paper becomes heavier when you roll it up, and we taped 2 rolled newspapers at the top of our structure...

which lead to DESTRUCTION! It didn't stand.

To fix our structure, we should've either made the base stronger/change the base, or not tape the rolled newspapers, because our middle newspapers were not strong enough to support it.

The winning group had a very strong base; it consisted of legs (tripod) that were rolled and had the most mass.

It was a good and fun experience to have everyone's input, although we failed :D!

Blog 1. Fun stuffs~

http://www.youtube.com/watch?v=AY9qcDCFeVI&feature=channel

LOLOL. What a waste of lemons, but it's nerdy and neat!

Blog 1.1 Note: Electrical Potential

Diagram: Voltmeter (parallel circuit)

• Work (energy required) must be done to increase potential energy. (i.e. work done by power supply to increase the electrical potentical energy from low -> high)
  
  
• As the charge flows through the load, its energy decreases.
  
  
• Energy delivered to load depends on energy per charge (see energy transferred by charge flow)
  
  
• Potential difference btw. any 2 pts. can be measured by a voltmeter (see diagram) and must be connected in parallel with a load.
  
  
• The voltmeter must be less than the load (in terms of conducting).

VOCABULARY4KIDS

electric potential difference (V): V = E/Q

where E is energy req. to increase the electric potential of a charge, Q.

(V)oltage = potential difference.

energy transferred by charge flow: E = VIt

where E = energy in joules, V = potential difference in volts, I = current in (A), t = time in sec.

Blog 1. Note: Current Electricity and Electric Circuits

Diagram: Parts of a circuit.

• Think of a cycle when thinking about electric currents.
  
  
• Red for positive (+) terminal, Black for negative (-) terminal, which is why wires are coloured to keep track of the direction of electron current flow.
  
  
• For electric current to flow, there needs to be a complete path from (-) side of power supply -> (+) side.
• Scratch that, now we've learned the Conventional circuit... which is the opposite: + to -
  
  
• THIS IS CALLED A CIRCUIT which is required for ANY electrical device to work properly.
  
  
• An ammeter must be an excellent conductor so that no energy is lost.
  
  
• There are too many circuit symbols to post here.
  
  

VOCABULARY4KIDS

electric current: the flow of charge/electrons.

Current is the rate of charge flow (I) : I = Q/t

I = current in amperes (A), Q = charge in coulombs (C), t = time in seconds.

Base unit for current: C/s

conventional current: the model of a positive charge flow

ammeter: a current-measuring device

direct current (DC): current flows in a single direction: power supply through conductor -> load, a device that uses energy -> power supply.

alternating current (AC): electrons periodically reverse the direction of their flow.

circuit: check abv.