Right Hand Rules #1 & #2

OERSTED'S PRINCIPLE: Charge moving through a conductor produces a circular magnetic field around the conductor

RHR#1



RIGHT-HAND RULE #1 (RHR#1) for conventional current flow: Grasp the conductor with the humb of the right hand pointing in the direction of conventional, or positive (+), current flow. The curved fingers point in the direction of the magnetic field around the conductor.



RHR#2



RIGHT-HAND RULE #2 (RHR#2) for conventional current flow: Grasp the coiled conductor with the right hand so that the curved fingers point in the direction of conventional, or positive (+), current flow. The thumb points in the direction of the magnetic field within the coil. Outside the coil, the thumb represents the north (N) end of the electromagnet produced by the coil.

Check out this awesome video:

Magnetic Force /Electromagnets

MAGNETIC FIELD: distribution of a magnetic force in the region of a magnet.
- Two different magnetic characteristics labelled North and South

- Similar magnetic poles, north and north or south and south REPEL one another with force
- Dissimilar poles, north and south, ATTRACT one another with a force

The law of magnetic forces

TEST COMPASS: a compass used to check for the presence of a magnetic field

FERROMAGNETIC METALS: metals such as iron, nickel, cobalt or mixtures of these three that attract magnets

DOMAIN THEORY: All large magnets are made up of many smaller and rotatable magnets, called dipoles, which can interact with other dipoles close by. If dipoles line up, then a small magnetic domain is produced.

Dipoles: the small and flexable magnets that make up a large magnet

Magnetic domain: the effect produced when dipoles of a magnet line up

Resistance/Ohm's Law/Kirchhoff's Law

RESISTANCE:  a measure of the opposition to current flow  

•  the amount of current flow in a circuit depends on two things: 

1)  the potential difference of the power supply
2) the nature of the pathway through the loads 

OHM'S LAW:

• Graphing the Linear Equation for Ohm's Law from Data:

• Factors that Affect Resistance:

- Length: longer the conductor, the greater the resistance
- Cross-sectional area: the larger/thicker conductor, less resistant it has to charge flow
- Type of material: resistivity is measure of resistance of a substance
- Temperature: greater molecular motion at higher temperature increases the resistance

• SUPERCONDUCTIVITY: ability of a material to conduct electricity without heat loss due to electrical resistance.

KIRCHHOFF'S CURRENT LAW:
The total amount of current into a junction point of a circuit equals the total current that flows out of that same junction.

KIRCHHOFF'S VOLTAGE LAW:
The total of all electrical potential decreases in any complete circuit loop is equal to any potential increases in that circuit loop.

• In other words, there is no net gain or loss of elecric charge or energy

Kirchhoff's laws in a SERIES circuit:
VOLTAGE: Voltage must be distributed so that the sum of all voltage drops must equal this value.

VT= V1 + V2 + V3

CURRENT: The circuit only has one path to flow.

IT= I1 = I2 = I3

Kirchhoff's laws in a PARALLEL circuit:
VOLTAGE: Voltage drops have to remain the same no matter what.

VT= V1 + V2 + V3

CURRENT: the sum of the current entering junctions must equal the sum of the current exiting them.

IT= I1 + I2 + I3

RESISTANCE IN SERIES:

RT = R1 + R2 + R3 .... + RN

(N is the total number of series resistors in the circuit)

RESISTANCE IN PARALLEL:

1/RT = 1/R1 + 1/R2 + 1/R3 .... + 1/RN

You can rewatch the video on RESISTANCE :)

Prelab Table

Completing the Circuit

What is the difference between a series and parallel circuit?

( A circuit is the path that electricity follows. )

All of the electricity
follows path #1

SERIES CIRCUIT: In a series circuit, the parts of the circuit (such as the battery, a switch, and the electric device) are connected one after another (in series) in a single closed loop. A series circuit allows electrons to follow only one path. The loads in a series circuit must share the available voltage. In other words, each load in a series circuit will use up some portion of the voltage, leaving less for the next load in the circuit. This means that the light, heat, or sound given off by the device will be reduced. If one device (e.g. bulb) in series burns out, the circuit is broken and there is no other path for the flow of charges therefore the other devices no longer work.

Some current follows path #1,
while the remainder splits
off from #1 and follows path #2

PARALLEL CIRCUIT: In parallel circuits, all the devices share a common connection to the voltage source. Different devices are on separate "parallel" branches. In parallel circuits, the electric current can follow more than one path to return to the source, so it splits up among all the available paths. Across all the paths in a parallel circuit the voltage is the same, so each device will produce its full output. There are different paths for currents such that a break in the flow of charges in one path does not interrupt the flow along other paths.

 

“To give an analogy of each circuit, in a series circuit, a postman has something to deliver to only one house; and in a parallel circuit, the postman has things to deliver to two houses. In a series circuit, if a part of the route gets destroyed, the postman cannot deliver whatever has to be delivered; in a parallel circuit, if one route becomes impassable for whatever reason, the postman can still reach one house.” - EC

Check out this awesome video on this topic.

Energy Ball Questions

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. By placing two of my fingers on both of the metal contacts on the energy ball, I am able to conduct electricity. This works because humans make pretty good electrical conductors. The human body is mostly water, plus salts, minerals and whole bunch of other stuff that makes that water very conductive to electricity. The electricity in my body flows to my fingers and gets transferred onto the metal contacts which takes the charge to the battery, resulting in current that makes the ball flash and hum.
Q2. Why do you have to touch both metal contacts to make the ball work?
I have to touch both metal contacts to make the ball work because the electricity from both metal contacts (terminals) help the charges flow endlessly to complete the circuit.
Q3. Will the ball light up if you connect the contacts with any material?
No, the ball only works when the contacts connect to conductors that are charged. Not every material is a conductor.
Q4. Which materials will make the energy ball work? Test your hypothesis.
Materials that will make the energy ball work are called conductors. A conductor is a material that has free electrons that allow the flow of electric current. Conductors such as metals and humans would make the energy ball work. My group had tested our hypothesis by using the metal hose nozzles for gas by the sink and making that material come in contact with the energy ball. Sure enough, as soon as both the contacts of the energy ball came in contact with the metal it began to hum and flash, proving our hypothesis to be correct.
Q5. This ball does not work on certain individuals - what could cause this to happen?
Although we could all successfully make the energy ball work, sometimes it would be a stronger hum and flash on certain individuals and weaker on others. I think this happens because like any conductive object, humans can store sizable quantities of electrical charge - the 'static electricity' that builds up on your body when you walk across a carpet. Simply, at that moment some people could be more charged than others.
Another cause could be something blocking the way of electricity to flow from the finger onto the metal contacts such as wearing gloves. The gloves in this situation act as an insulator which is a substance that resists the flow of electric current.
Q6. Can you make the energy ball work with all 5-6 individuals in your group? Will it work with the entire class?
Yes, our group made the energy ball work. Two members would touch either of the contacts and we allowed electric flow by touching each other’s fingers.
Yes, it works with the entire class. This was proven when Mr. Chung had given the class the challenge to do so. Everyone connected with each other by touching fingers while two classmates touched the metal contacts of the energy ball. As soon as the circuit was complete, in other words, as soon as everyone was connected, the energy ball began to hum and flash.
Q7. What kind of a circuit can you form with one ball?
A series circuit is formed with one ball.
Q8. Given 2 balls: Can you create a circuit where both balls light up? (1/3)
Yes, we can create a circuit that lights up both balls using the same method mentioned in Q6.
Q9. What do you think will happen if one person lets go of another person's hand and why? (2/3)
If any person lets go, the circuit would be “opened” thus breaking the flow of electrons, meaning that the energy ball would not work. In a series circuit such as this, everyone must be connected to complete the circuit.
Q10. Does it matter who lets go? Try it. (3/3)
No, it does not matter who lets go. In a series circuit, it’s essential for everyone to be connected or else the circuit would be disrupted and the electric current would have to stop since there is no where for it to flow continuously.
Q11. Can you create a circuit where only one ball lights (both balls must be included in the circuit)? (1/2)
Yes, using a parallel circuit.
Q12. What is the minimum number of people required to complete this? (2/2)
The minimum number of people required to complete this is 4.

Physics of Tall Structures

There are a great many things about architecture

that are hidden from the untrained eye. 

- Frank Gehry

What makes a tall structure stable?

I find pretty much all buildings beautiful.

Certain buildings inspire many feelings and emotions in us from old buildings, a reminder of history, or even tall buildings, admiring and applauding how it could possibly stand with such an incredible height. Yeah, I get that emotion when I regularly pass by our CN tower.  

Looking at these comparisons of the tallest
 structures in the world, you can notice how
most have a strong definite wide base
and triangular shapes in their designs.

I think the main component for a strong, sturdy structure would have to be its base. Starting off with a strong base not only assures that the building can increase its height but it also avoids any doubts of the building crumpling down. The base in most tall structures seem to be wide so that they could easily distribute the mass better.

Great Pyramid of Khufu

As well shapes are a big factor for structures and triangles seem to work the best. If you look around, you will notice that most of our buildings are shaped like rectangles and squares. However, if you look closely, you will see that those buildings use triangles. Triangles are the strongest geometric shape in the world. Its shape is very simple: a flat base with two sides that come together at the top to meet at a point. They are rigid, able to stand freely, and able to support their own weight. Triangles are so important in structure design that even many years ago in Ancient Egypt, builders designed huge pyramids with the shape of a triangle in mind. One of the oldest pyramids in Egypt is called the Great Pyramid of Khufu. It was built around 2575 BC. This pyramid is one of the largest surviving pyramids in the world today. I'm guessing future architects examined these ever lasting structures and learned that the triangle shape is the way to go.

Lastly, weight distribution is a huge important factor for tall structures. Would you ever build a building from cardboard at the bottom and the upper ones from brick? Probably not since you'd run into problems quite quickly. Weight distribution from heavy to light helps a building balance and support its own weight.
 

What is the centre of gravity?

The center of gravity is the average

location of the weight of an object

OR

The place where an object's mass

seems to be the most concentrated.

GRAVITY: the magnetic-like force of attraction between any two objects in our universe.

On Earth, gravity seems to be the way that things fall to the floor, but gravity always work two ways. If you drop a pen, it does fall toward the floor—but the floor also jumps up by a microscopic amount to meet it on the way. The force pulling your pen down toward Earth is exactly the same size as the force that pulls Earth up toward the pen.

Different people have different centre of gravity.
For example the baby has a heavier head
than body so its centre of gravity is higher.

Now gravity usually pulls things straight downward, but it can act in other ways too. Suppose you built a really tall brick wall. We can think of gravity acting on it in two different ways. We can see it as a collection of separate bricks, with gravity pulling on each one separately. Or we can think of it as a solid wall with gravity pulling on the whole thing, just as though all its mass were packed into a single point in its center. For a simple brick wall, the center of gravity is right in the middle of the central brick.

If the center of gravity is over to one side (if we've not built the wall straight or if we've built it on sloping ground), the force of gravity acting down will produce a turning effect called a moment. If the moment is small, the mortar between the bricks can resist it and keep the wall upright. But if the moment is too large, the mortar will break apart, the bricks will topple, and the wall will collapse.

Now this doesn't just apply to single walls: it applies to entire buildings. That's why tall buildings need deep foundations (where a significant part of the building is constructed underground to support the part that's above ground). If something tries to push the top the building to one side, the foundations effectively resist and push it back in the opposite direction. In other words, they help to counter the moment that would make a building topple to one side.

Check out this website for awesome info on this topic.

How High Can You Go?

Challenge: To build the tallest structure you could possibly make out of newspaper and tape, in only 20 minutes.

Check out our
beauty of a structure :)

After endless hours (more like a few minutes) of planning the design and structural form of the building, my group came to the final decision that this wasn't going to be easy.

Looking around, we saw that some groups had already begun building right away and others were still planning. The main shape that was common among all groups was the triangle. Previously knowing that triangles are the strongest shape, as a group we agreed on using it for maximum strudiness of our structure. We divided the work, leaving the base arrangment up to me and the height up to my group members. Going with the idea of a triangular base, we began unsuccessfully rolling the flimsy newspaper into cone shapes. Immediately it was evident that a strong triangular shape wasn't going to magically be made from the newspaper. Since there was no other shape in mind that could have been a base and with such short allotted time we decided to just stick with a weak cone shape foudation. A weak base is better than no base  ... right?

As for the increasing body and height of the structure, we came up with the idea of rolling each newspaper into a cylinder and as the height increases the diameter of the cylinder would decrease. This idea is similar to the "Nested Doll Principle" or "Matryoshka Principle".

Do you know those wooden Russian dolls that when you seperate the first doll, it reveals another doll smaller than the one before, which has another doll inside her and so on? Yeah, those are adorable. (: Anyways, our building was similar to that as the cylinders kept on decreasing in diameter and and had one cylinder inside another. This way the mass of the structure would be more balanced with more weight at the bottom and less on the top.

Rushing to finish our structure and admiring the fact it actually stood still by itself,
it was promptly punched down by  Mr. Chung. Thanks a lot.

Overall, I enjoyed this challenge because I LOVE building things. Of course, I'd rather we'd have more time and better material but that made this challenge more demanding and visionary.

Blog 1: Notes on Current Electricity

• An ELECTRIC CURRENT is a flow of microscopic particles called ELECTRONS flowing through a conductive material (usually a wire)

Simple electric current

• CURRENT: Total amount of charge moving past a point in a conductor divided by the time taken

      I = Q/t

where ... I = current in amperes (A)

                Q = charge in coulombs

                t  = time in seconds

@5:58: CURRENT explained.

• The direction that the current flows is from the negative terminal to the positive terminal

There are TWO types of electric currents:

• DIRECT CURRENT (DC) : current always flows in the same direction between the positive and negative terminals of a power supply to a load (device that uses energy)
• ALTERNATING CURRENT (AC) : the direction of the current reverses with the support of electric and magnetic forces
• Electric current is measured in amps (A) using an anmeter connected to the complete path of current called a circuit

If you could SEE the electric currents in a wire, they would look something like the following:

DIRECT CURRENT

ALTERNATING CURRENT

• ELECTRIC POTENTIAL DIFFERENCE (V): the electrical potential energy for each coulomb of charge in a circuit 

V= E/Q

where ... E = energy required to increase electric potential of a charge 
                Q = amount of charge
                V = the volt is the unit used to measure electric potential difference 



@6:30: Electric potential difference explained.

• ENERGY TRANSFER:

E = VIt

where ... E = energy in joules
              V = potential differencein volts
               I = current in amperes
              T = time in seconds  

• Voltmeter measures the potential difference between any two points, provided that it must be connect in parallel with the load in the circuit and had a large resistance so that its measurement will deflect a minimal current from the circuit