ENERGY

LAWS OF ENERGY
1. Conservation of Energy
2. Law of Entropy
3.Absolute Zero

The first law of thermodynamics says that energy cannot be created or destroyed. Energy can be transformed and transferred.

Many different types of energy exist:

 

• kinetic energy
• gravitational potential energy
• mechanical energy
• chemical energy
• electrical energy
• light energy
• heat energy
• sound energy
• elastic energy
• nuclear energy

 

Kinetic energy describes movement.  

On the other hand, gravitational potential energy is energy due to an object's distance from the ground. This is usually measured when the object is static.  

Gravitational potential energy and kinetic energy combine to form mechanical energy. Mechanical energy is energy produced due to the movement of objects. Mechanical energy assists many machines.Some simple machines aided by mechanical energy are are incline plains and levers. Other machines that make use of mechanical energy are pulleys and screws.

 

Chemical energy is caused by chemical reactions. It  can be called chemical potential energy because there is energy stored in the molecular bonds ready to be used.

 

Electrical energy is caused by charged particles that produce an electrical current. The particles are always moving. On a molecular level this type of energy is kinetic.

 

Light energy is a form of kinetic energy that emits light (visible or non visible to the naked eye).  Sometimes, light energy goes hand in hand with heat energy. 

Heat energy is energy stored in objects above absolute zero. This would comprise of all objects. Heat energy can be either potential or kinetic.When an object is heated, the particles in the object contain more energy and bounce off each other faster. On a molecular level heat energy is kinetic.

 

Sound energy is energy caused by vibrating object. Vibrations are movements of waves in the air. In this sense sound energy is kinetic.

Elastic energy (i.e. spring energy) is potential energy.  It is shown whenever and object is stretched. Springs get either compressed and pulled. Elastics can be stretched out. When someone points a stretched elastic at you , it is an instinct to pull away. This is because people are aware of potential of the elastic to hit you.

 

Nuclear energy energy that is stored in atoms. Nuclear energy is a form of potential energy. Nuclear fusion and nuclear fission are the two types of nuclear energy. Nuclear fusion is a combining of atoms. Nuclear fusion releases a certain amount of energy.  Nuclear fission is the opposite; atoms are split instead.

 

Energy is essential to our lives and well being. Without it, we cannot form chemical bonds in our stomachs and digest the food we eat. Likely without energy we would not exist due to absolute zero. It is important to remember that energy is never lost. It is transformed into different types of energy.

CANNONS

The third class assignment we completed was building a cannon.

This is what we built, kind of. Except that we made it out of popcans.

Cannons are capable of creating a lot of destruction by shooting out cannon balls or simply investing more energy into making much noise. Either way, a real cannon might seem intimidating, which is probably why many ancient battle tactics involved cannons. They had a wide variety of purposes, some of the most common ones involving sinking enemies ships or conquering strongholds.

By analyzing the reason why cannons were so popular we must look at the the way they achieve theirr parabolic motion. Cannons make use of projectile motion. Cannons make use of parabolic motion (due to a vertically shot cannon ball which is brought down by gravity.) Cannons also display the transformation of chemical potential energy into sound energy, kinetic energy, heat energy and work done.

In Kinematics we learned a formula that calculates the range of a projectile.
The velocity in the x-axis is constant because of negligible air resistance. We cannot assume there is no air resistance, however it is low enough not to make a difference in the long run.

The initial height of the projectile is from the ground, thus 0 metres in displacement in the y component. This is not exactly how our cannon operated however, because we raised up the opening where the cannon ball was shot out by about 25 cm.  As well, the optimum angle to shoot the cannon ball at is 45°. This is explained due to the parabolic motion of the cannon ball. The cannon ball will not be shot too low (resulting in a short flying time) nor will it be shot too far up, resulting in a short distance traveled horizontally. If the cannon is shot at a great angle up (e.x. 80°  the range might just be close to 0 metres.) The projectile will be in a parabolic motion, therefore the maximum range might be obtained if the cannon makes a 45° with the ground.

Other factors can contribute to a greater range.  The cannon ball should be as light as possible. The force applied on the cannonball is constant. The mass of the cannon ball is inversely proportional to the acceleration. If the mass of the cannon ball is lighter, a higher acceleration will be achieved. Lastly, the projectile should launched from a longer barrel of the cannon, with more baffles.  more energy will be stored before the cannon is launched. The ethanol will have more surface area to spread over, and therefore it will have the ability to make more connections with air. By increasing the action force acting on the cannon, the reaction force will also increase (equal and opposite reaction force.) This exemplifies Newton's Third Law.

NETON"S THREE LAWS

Newton's Three Laws are:

1. The law of Inertia.  Objects will continue to be in motion or stationary unless it is affected by another force against it.
2. Force=mass . acceleration.  Force is directly proportional to mass times acceleration. Mass and acceleration however share an inverse relationship.
3. For every action force, there is and equal and opposite reaction force. (However it is possible for the reaction force to act in the same direction as the action force. For example if a person with skates is standing constant on ice, and another person skating bumps into the stationary person, the reaction force will send the stationary person in the same direction as the skating person was traveling.)

Four types of problems involving Newton's Three Laws:

1. Equilibrium

Equilibrium is when the object remains static.  These are the assumptions made when solving equilibrium problems:

• there is no friction
• there is no acceleration
• the net force is 0

2. Inclined Planes

There are incline problems can be solved in two ways. (Those involving a static Mk and those involving a  kinetic Mk.) Incline plane problems involves friction because the object is sliding down a slope (hence the name inclined plane). The object has a friction because since the surface is slanted there is a force applied in the x-axis. Friction resists the force. Assumptions to be made when solving incline plane problems are:

For static:

• there is no acceleration
• the positive axes is the direction of acceleration on the surface
• there is no air resistance
• Mu is static if the object is not moving at first
• the normal force is perpendicular to the surface

For kinetic:

• The normal force is perpendicular to the surface
• there is acceleration
• there is no air resistance
• Positive axes are in the direction of acceleration and surface
• Mu is kinetic if the object is moving

When solving incline questions FBDs can be really helpful.  Gravity is always pointing down.  Gravity should be broken down using x and y components.

3. Pulleys

The assumptions when solving pulley problems are:

• the pulley has no friction
• the rope is frictionless
• there is no air resistance
• there are 2 FBDs (one for each load)
• tension for both systems is equal
• Acceleration of the 2 systems is the same
• Positive axes are the direction of the acceleration of each load

4. Trains

Assumptions for train questions:

• there is no air resistance
• there is the same acceleration throughout the whole system
• the y component is in equilibrium (no acceleration) 
• FBDs one for each of the masses
• The cables that connect the masses are weightless
• Positive axis is in the direction of  the acceleration

There are also tension forces connecting the carts. For example the tension force pulling cart 3 forwards is the same as the tension force pulling cart 2 backwards.

Assumptions are very important to include when solving the four types of problems, because it is necessary to specify the conditions concerning a problem in order to find a way to solve it.

Projectile Motion

The key to solving two-dimensional problems is to break them up into two one-dimensional parts, then recombine them to produce a final answer. You will have a set of givens in the x-direction and another set in the y-direction.

Projecto shot horizontally:

a_x =0                                          a_y =  - 9.8 m/s²

v_x = constant                              v_y changing

Δd_x = range                                Δd_x = height

Use the formulas:

Δd_x= v_x Δt                                  Δd_y= v_y Δt + ½ a_y Δt²

If you can find the Δt in x direction, then transfer it in the y direction and find the height.

If you can’t find Δt in the x-direction calculate it in the y-drection, and then transfer it to y-direction to find the range.

The Physics Behind Roller Coasters

The roller coaster is driven almost entirely by inertial, gravitational and centripetal forces.
The train is moved by gravity and momentum. When a coaster has reached the highest point along its course, normally a tall hill at the beginning of the circuit, gravity is what provides the force that controls the speed of the ride.  Inertia is the reluctance of a body ( for example, a coaster train) to change its direction of motion. A coaster train that is accelerating down a steep hill will resist the change in direction and head up the next hill.

But before the train can gain momentum and take advantage of gravitational forces, it needs an initial push to get up the hill.
A chain loop can be used to move the train up. This can consist of a gear at the bottom attached to a motor that moves the roller coaster up.
A catapult launch can build up a great amount of kinetic energy over a short time.

The potential energy the roller coaster builds going up the hill is released as kinetic energy, the energy of motion that takes the coaster down the hill.

The coaster tracksare important in channeling the force. They control the way the coaster cars fall. If the tracks slope down, gravity pulls the front of the car toward the ground. The coaster therefore accelerates. If the tracks tilt up gravity applies a downward force on the back of the coaster. The coaster decelerates.

An object in motion tends to stay in motion (Newton's first law of motion.) The roller coaster car will maintain a forward velocity even when it is moving up the track. This movement is opposite the force of gravity. When the coaster ascends one of the smaller hills that follows the initial lift hill, its kinetic energy changes back to potential energy. It is back at the top. The course of the track is constantly converting energy from kinetic to potential vice versa again.

In most roller coasters, the hills decrease in height as they progress along the track. Thsi happens because the total energy reservoir built up in the lift hill is gradually lost to friction.There is friction between the train and the track and between the train and the air. When the train reaches the end of the track the energy reservoir is almost completely empty.

Roller coasters have brake systems. Those brake systems however, are not situated on the coaster itself, but on the tracks. There are a series of clamps built into the track of the train. There is a central computer system which operates the hydraulic system and closes the clamps for the train to stop.


To sum it all up , when a coaster is at the highest point of its track, there is a high potential energy This can be referd to as energy of position. When the coaster accelerates down the hill the potential energy changes into kinetic energy (or energy of motion). Each time the coaster goes up another hill, the kinetic energy turns into potential energy again. The cycle continues. Ideally, the total amount of energy would remain the same. However some is lost to friction between the wheels and the rails. There is wind drag along the train, and also friction applied by the brakes. Due to this energy loss, each successive hill along a coaster track needs to be smaller than the previous hill to allow the train to continue along the course.


Safety Features
By the nature of the laws of physics a roller coaster wants to fly off the track. Any accidents are prevented by the wheel design and the track.
The weight of the train is supported by running wheels (the largest wheels.)
On the sides of the coaster train guide wheels are arranged to provide stability during tight turns and to keep the coaster train from rubbing the structure of the ride.
Upstop wheels are smaller wheels. They are on the underside of the rails that keep the train locked to the track and allow the train more airtime because they eliminate the danger of the train leaving the track.
A rollback can occur when a coaster fails to crest a hill. Instead, it begins to move backward. Coaster trains are equipped with anti-rollbacks paired with the chain dogs. A rollback can be caused from too much gravity.




check out these websites for more information
http://tlc.howstuffworks.com/family/roller-coaster3.htm
http://www.essortment.com/hobbies/rollercoasters_sdzq.htm

How To Add Vectors

For scalar quantities there is no question about the final result of adding two quantities. For vector quantities the value depends on the direction and angle between the two vectors. The resultant vector of the addition needs to be specified by a magnitude and direction. It is called total displacement.

The vector direction needs to be shown in relation to North and South.
If you know the angle from North or South to the direction, use trigonometry to solve for vertical and horizontal displacement.
Use sin and cos to find the horizontal and vertical distance.
Record the distance in a table with a positive sign if N or E and a negative sign if S or W.
Add up the total displacement horizontally and the total displacement for each vector. (This is similar to collecting like terms in math.)
Once you have the total horizontal and vertical displacement you can find the length of the distance and direction.
Use Pythagoras' theorem for length and the tan function for direction and angle compared to N or S.

If you know the length of a bunch of vectors and directions in relevance to North and South it is possible to find the total displacement horizontally and vertically. This can be done using cosine and sine function of an angle, and the hypotenuse. When the total horizontal and vertical displacement of all the vectors are found, they need to be added up. This will give us the two legs of the triangle. Knowing the two legs' length will make it possible to fine the hypotenuse using Phythagoras' theorem. The angle of the final displacement, in relevance to North and South can be found by using the tangent function.
It is important to split up vectors in horizontal and vertical displacement when adding the total of the vectors, because that way all of the directions are the same. It is possible to add them together. Otherwise the vectors would be going in different directions, and when added up would give a not accurate result. By splitting up vectors into horizontal and vertical it is also possible to assign a positive and negative direction.

Deriving Equation Four

Equation four can be derived from the velocity time graph by deriving the first two equations and then manipulating equation 2 so that it can be substituted into equation 1. From equation 2, the V1 value is isolated.

from equation 2
a = (V2 - V1) / Δt
a . Δt = V2 - V1

plug this into equation 1
d = 1/2 (V1 + V2) Δt
d = 1/2 (V2 - a . Δt + V2)Δt
d = 1/2 (2V2 - a . Δt) . Δt
d = V2 . Δt - 1/2 . a . Δt²
This equation is only applicable in problems involving constant acceleration, because it was derived from a graph involving constant acceleration.

Equation 4 can be proved from the velocity time graph.
The area from the graph to the x axis is equal to the total distance.
If velocity two is more than velocity one, then by calculating V2 . t we find the area of a rectangle that would give the distance traveled at a constant velocity of the faster speed.
However the speed was not always the faster speed. It  started of slow and accelerated from V1 to V2.
Therefore we need to subtract the area of a triangle that is not part of the graph. This area is equivalent to 1/2 of the rectangle formed between the difference of V2 and V1 multiplied by the time taken.

Equation Three

There are five equations that can be derived from a velocity time graph. This applies to motion that has a constant acceleration

The first two equations are
1. V2 = V1 + a .Δt
2. d = 1/2 (V2 + V1) Δt
The following three equations can be derived from the first two by rearranging the variables. This is done by isolating each of the variables in the first equation and plugging them into the second equation.
3. d = V1 . Δt  + 1/2 . a . Δt
4. d = V2 . t - 1/2 . a .Δt
5. V2²  = V1 + 2 . a . d

Equation One
The velocity at a certain point in time is equal to the initial velocity + (the acceleration in seconds squared times the change of time in seconds)
V2 = V1 + a . t
Find the slope of the graph.
The rise is V2 - V1
The run is the change in time

Equation Two
The area (of the trapezoid) calculated in this equation is the change in distance.
the base = time
heights = V2 and V1
d = 1/2 (V2 + V1) Δt
Now that we have equation 1 and equation 2 we can find equation 3.

Equation 1
V2 = V1 + a . Δt
V2 is ready for substitution into Equation 2.

d = 1/2 (V2 + V1) Δt
d = 1/2 ( V1 + a .Δt + V1)
d = 1/2 (2V1 + a .Δt)Δt
d = V1 .Δt + 1/2 . a . Δt²           < Equation 3

This can be proven from the velocity time graph.
The graph can be split into a reactangle and a triangle on top of it.
Distance is equal to the area of the reactangle from where the slope starts, and the triangle on top of it.
the area of a triangle can be found using the formula
d = 1/2 (V2- V1) . Δt
The area of the rectangle can be found using the formula
d = V1 . Δt
Putting the two together gives equation 3

We can find three equations from equation 1 and 2, just like we found equation 3 by
isolating V1 in equation 1
isolating V2 in equation 1
isolating Δt in equation 1
This is how we can get the five fundamental equations in kinematics!

Motion Graphs

This was our first distance over time graph. The distance started at 1 m. The distance increased over the first 3 seconds, it plateaued for 3 seconds, and then it decreased to 1.5 m where it stayed for about 3 seconds.
The velocity was positive and constant for the first part of the graph. From 3 - 6 seconds the velocity was 0, followed by a negative velocity for 1 s, and then 0 velocity.
The acceleration for this graph was 0.

The second graph is also a time vs. distance graph. The motion can be described as start at 3 m from the motion detector. Walk away for 2 s. Stay for a second. Walk away for a second. Present position=1.5 m. Stay at 1.5 m for 2 s. Then walk back to 3 m for 3 seconds.
The velocity is positive for the first 3 seconds. Then velocity becomes 0 because there is not movement. For 1 second again there is a positive velocity followed by a zero velocity. For the last 3 seconds there is a negative velocity because there is movement away from the origin and opposing the original direction of movement.
There is no acceleration in this graph.

Our third graph was time vs velocity. The initial speed was 0m/s for 2 seconds. During seconds 2 - 5 the speed becomes 0.5m/s. The speed goes back to being 0 m/s for another 2 seconds. The speed for the last 3 seconds reverses direction and becomes 0.5m/s (in the opposite direction of the initial speed.)
The distance vs. time graph version of the graph above would have a line on the x-axis for the first 2 seconds, followed by a positive slope for the next 3 seconds, that reaches from 0 to 1.5. There would be a line at 1.5 parallel to the x-axis for 3 seconds, and then a line that has a negative slope and reaches from 1.5m on second 7  to 0 m on second 10.
The acceleration graph would have a 0 slope, and can be graphed on the x-axis.

Graph number four shows velocity vs. time. The velocity starts off as 0 and accelerates in a positive direction for four seconds, until it reaches 0.5 m/s.The velocity stays at 0.5 m/s for 2 seconds. At 6 seconds, the velocity drops down to -0.4m/s and remains like that until the 9th second, when the movement stops, and velocity is 0.
The distance reached from the origin of the graph in the first 6 seconds is 2m. Then over the next 3 seconds the distance decreases by 1.5 m and the position is 0.5 m. The distance remains 0.5 m for the last second.
The acceleration for the first 4 seconds of the graph is 0.125m/s. It is positive. There is no acceleration for the rest of the graph.

The fifth graph is a position vs. time graph. The position starts at 0.8m and over the first 3 seconds the position increases steadily going up to 1.8 m. The distance remains 1.8 m for about 4 seconds. After 4 seconds, it increases steadily up to 2.5 m over a 1 s. time period.
The velocity for this graph starts off as positive at about 0.3 m/s for about 3 seconds. Then the velocity remains 0 for four seconds. This means there is no movement. The velocity becomes 0.5m/s for the last second.
The acceleration for the whole graph is 0. There is no increase or decrease in speed.

The graph above shows a velocity vs. time relationship. At first the velocity is less than 0.5 m/s. This lasts for about 3 seconds. Then the velocity becomes a little over -0.5m/s. The velocity stays at this rate for about 4 seconds. Then at 7 seconds, the velocity becomes 0m/s.

First there is a movement of 1.5 m in 3 seconds. This is followed by another movement of 2 m over 4 seconds, in a contrary direction. After the initial 7 seconds, there is a plateau in distance and no movement for 3 seconds.

There is no acceleration in the above graph at an part.

Bulding An Electric Motor

Thursday September 30, 2010

Today the class had to build an electric motor.

The materials we used were, a power supply, paper clips, an axle, commutator pins, cork, armature wire, nails, thumbtacks, strips made from aluminium cans, and magnets.
The motor itself was made out of a cork tap, and coil wrapped around it.

Wire was filed at the ends and twisted around the cork. The ends were filed down, so the wire would conduct electricity at the part where it was connected to the commutator pins.
The motor was stuck on an axle and supported up by paper clips.
Commutator pins were placed at ends of one of the faces of the cork tap in a way that when the cork span, the two commutator pins touched the aluminium strips (brushes). The purpose of the aluminium and the commutator pins was to pass on a current which made the motor spin.

When we wound the piece of wire around the cork tap we were able to use up most of it, however we had to cut a small portion. If we used more of the wire, the motor would have spun more easily. It is possible that the ends of the wire were not touching the commutator pins, or were not properly sanded down, which caused the current to not complete its circuit.
When we nailed the four inch nails, we left too much space and had to re-hammer them closer together, so the magnets would stick. We did not hammer them down very well, and the construction was unstable.
There was another problem with our motor. The strips of aluminium we cut out were too long and thin. They ended up getting caught in each other on top and not touching the commutator pins properly.
The commutator pins we used were too short. They did not contact the aluminium strips. When they were in the cork far enough to be stable, they did not reach all the way to the aluminium strips. We realized we needed to improve the motor.
Tonight we will work on rewinding the coil, and filing down the wire to make sure that the current is passing through the motor so it can spin. We will also cut out more stable strips of aluminium and longer commutator pins, so that they contact each other.
Also we will add something on the ends of the axle so that the motor does not move up and down the paper clip supports. We want to make sure the motor spins at a stable spot, so that it touches the aluminum strips, every time it makes a turn.
Another change we will make is to make the holes inside the paper clips larger, so that they offer less resistance to the axle of the motor when it spins.

Hopefully by making those changes, our motor will work and everything will be fine with our motor.

One thing that we did nicely was to keep our board clean and organized. The motor was attached on the axle nicely. The paper clip supports were even.
Motor principle refers to the force produced between a magnet and an electromagnet. An important application of this principle is the electric motor. It directs electric force full circle.

These are pictures of our motor in the process.

Sunday October 3, 2010

By Friday, we had completed our motor and tested it in class. We were excited to see if the improvements we worked on would really make our motor work more smoothly and perform better.
When we attached the magnets and power supply we were disappointed because our motor did not spin.
At first we thought the problem was with the strips of the soda can and the coil. We were about to take off the coil and sand the edges better to allow for better conductivity, when Mr. Chung found out that there was something wrong with the wires used to connect our motor to the power source.
We were happy that our hard work payed off.

This is a picture of our completed motor before we tested it. It was spinning very smoothly.

Magnetism and Electromagnetism; Right Hand Rules

Oerstead' Principle; the charge moving through a condutor produces a circular magnetic field around the condutor.

RHR1
Grasp the conductor with the thumb of the right hand pointing in the direction of the conventional (positive) current flow. The curved fingers point in the direction of the magnetic field (around the condutor.)

RHR2
Grasp the coiled coductor, with the right hand. The curved fingers should point in the direction of the conventional (positive) current flow. The thumb should point in the direction of the magnetic field within the coil. The thumb also represents the north (N) end of the electromagnet produced by the coil.

Magnetism and Electromagnetism

- A magnetic field is the distribution of magnetic force in the region of a magnet.

- North and South are the two different magnetic characteristics. They are responsible for magnetic force.

- Similar magnetic poles (i.e. north and north, or south and south) repel one another.

- Dissimilar poles (north and south) attract one another with a force at a distance.

- To map a magnetic field we need to use a test compass.

-The Earth acts like a giant magnet, producing its own magnetic field. It is suggested that this magnetic field is produced because of the flow of hot liquid metals inside Earth.

- Magnetic forces act on ferromagnetic objects (certain metals that are not magnets.) Some ferromagnetic metals are iron, nickel, and cobalt. They have atomic structures that make them strongly magnetic.

-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 the dipoles line up, then a small magnetic domain is produced.

Resistance - Ohm's Law

 

The amount of current that flows through a circuit and the amount of energy transferred to any useful devices is dependant on the potential difference of the power supply and the nature of the pathway through the loads that use the potential energy.

 

The more difficult a path is, the more opposition to the flow there will be. The measure of this opposition is called the electrical resistance.

 

                  Resistance = Voltage / Current     or        R= V / I

 

The measure of resistance of a substance is called the resistivity. It has units called the ohm.

Resistance depends on a conductors' length, cross-sectional area, the material it is made of, and its temperature:

 

• A larger cross-sectional area of a conductor offers less resistance to the charge flow.(If the cross section is doubled, then the resistance goes to half of its original value.) 
• A longer conductor has greater resistance than a shorter one. (If length is doubled, then the resistance is also doubled.)
• Generally an increase of temperature of a conductor, usually contributes to an increase in the resistance but not for all substances.

 

In a series circuit the loads are connected one after the other.

 

In a parallel circuit the loads are connected side by side.

 

In any circuit, there is not net gain or net loss of energy.

 

Resources:

 

Ohm's Law and Resistor Circuits
Ohm's Law
More on Ohm's Law

PreLab Table, September 13, 2010

In Class Challenge 10/9/2010 and Parallel vs Series Circuit

The major difference between a parallel and a series circuit is in the way that the loads are connected. In a parallel circuit the loads are placed side by side.

                                           

In a series circuit however, the loads are connected one after the other in one path.

Each arrangement has an effect on the way in which potential difference and current act in the various parts of the circuit.

Kirchhoff's Current Law

The total of the current that flows into a junction point of a circuit is equal to the total amount of current that flows out of that same junction.

Kirchhoff's Voltage Law

The electric potential difference (voltage) of the battery (energy source) is equal to the total of the electric potential differences of the loads combined.

Kirchhoff's laws help us determine that in any circuit there is no net gain of electric charge or any net loss of energy.

In Class Challenge

Our class was split into groups of four and given an energy ball each.

My group could make the energy ball work by placing our finger over the hole that separated the two pieces of metal. The ball began to flash and hum because that way the circuit was completed.

A finger is a conductor. A metal is a conductor. By connecting the two pieces of metal with our fingers, we let the electrons flow and finish the circuit. We had to touch both metal ends, because by only touching one, the circuit does not complete.

The ball will not work if you connect the contacts with any material. For example, it will not work with glass, plastic, rubber, air, or wood. The material used has got to be a conductor of electricity.

About Conductors 

Conductors vs. Insulators

The energy ball works with anything that allows electricity to pass through. The material has to be a good conductor, for example, silver, gold, copper, aluminium or any other metal. According to the results of the activity, human skin completes the circuit and allows electricity to pass and is therefore a good conductor.

The ball does not work on individuals who try to close the circuit with their hair or clothes. That is because water is lacking. Water acts as a conductor only when metallic solids are present in the water (so that the water is charged and the particles are free to move.) The ball might not work on individuals with a certain condition or disease or dehydration.

For more information see: Is water a conductor of electricity?

The ball lights up with all four individuals in my group if we connect the circuit properly (complete the circuit.)

With one energy ball we can create a simple circuit. All the parts are simply connected.

Given two balls we can create a circuit where both balls light up. We can form a series circuit.

if one person lets go of the other person's hand (while they are acting as a part of the circuit) they will act as a switch and make the ball go off.

It does not make a difference of who lets go of the other person's hand. Circuit is broken nevertheless, if it is a series circuit. In a parallel circuit it is possible to have one energy ball on and the other off.

It is possible to create a circuit where only one ball lights up. This can be achieved by making a parallel circuit.

The minimum number of people needed for this circuit is four.

Resources:

Source 1 for Pictures

Source 2 for Pictures

Kirchhoff's Law

9/8/2010 In Class Challenge

In this challenge the class was split up into groups of three people and had to build the tallest structure, using a piece of tape and five pieces of newspaper. The rules were that the structure had to stand up by itself and be portable. The tallest structure built was around 160 cm.
My group first tried to make a structure out of rolling the pieces of newspaper into equal cylinders and stacking them on top of each other. That did not work however, because firstly, the pieces were very not stable, and the structure was too heavy at the top for the base to support it. We rolled the paper at the top, adding unnecessary weight. In addition we did not use the tape very reasonably, because in the end we were left with parts of the structure's top that were not stuck together properly and kept breaking. We set two pieces of newspaper aside for the base which we rolled into a ball and stuck the tower of our structure in. Because we could not stick the base to the ground our structure ended up falling.
I noticed that most of the successful structures in the class (i.e. the tall and stable ones) had a tripod base.

If I had to redo the challenge i would put less weight on top of the structure (by rolling half a piece of paper instead of a full one), and make the base wider.

Physics of a Tall Structure
- wide base
- use of triangles
- heavy base
- adding more support points
- taper the structure by making the top less heavy and skinnier
- a lower center of gravity makes it easier for the building to balance

The center of gravity(often called the center of mass) is the mean location of the mass in a structure. In order to stabilize a structure, engineers need to locate the center of gravity of a structure, and also distribute the mass of the structure evenly around it. The force of gravity acts on everything (i.e. all parts of the structure) so if the weight of the structure is distributed around it evenly, the structure will be stable.

For structures built outside the foundation on which they are built must be stable. The foundation must not be very moist. Also if the type of foundation is not taken into account, the structures may get cracks in their walls and the foundation.

Resources:
http://www.edquest.ca/component/content/article/156
http://www.grc.nasa.gov/WWW/K-12/airplane/cg.html
http://wiki.answers.com/Q/What_makes_a_structure_stable
http://wiki.answers.com/Q/What_are_some_ways_you_can_make_a_structure_more_stable
http://www.allenandunwin.com/_uploads/BookPdf/TeachersReview/9780713676884.pdf

Current Electricity and Electric Circuits

Physical Quantities and Measurements:


          Charge (Q) measured in coulombs (C)


          Current (I) measured in amperes (A)


          Time (t) measured in seconds


          Electrical Potential Difference (Voltage) measured in volts (V)


          Energy (E) measured in joule (J)



Facts Learned:

•  Current is the total amount of charge in Coulombs that goes through a point in a conductor, divided by the time it takes. Current is symbolized by I. The formula is:
 I (Current in Amperes) = Q (charge in Coulombs) divided by t (time in seconds) or I = Q / t

• The base unit for current is C/s which is named Ampere. It is represented by (A). One ampere = one Coulomb of charge moving through a point in the conductor / second.

• Conventional current flow vs. electron flow:
              - Conventional current flow is from positive to negative.
              - Electrons are negative and flow from negative to positive.

• Voltage vs. Current

              - Voltage is the electrical potential difference between two points.
              - Voltage would move from a point of higher potential to a point of lower if given the chance (until the levels equalize).
              - Current is the rate of flow of charge.

• In coloured writing convention used to keep track of electron current flow, black represents the negative terminal and red represents the positive terminal.

• In a direct current, the current flows in one direction. It flows from the power supply, through the conductor, to a load, and back to the power supply.

• In an alternating current the electrons reverse the direction of their flow periodically, with the help of electric and magnetic forces.

• Work is done by the power supply to increase the electrical potential energy of each coulomb of charge from a low to a high value. As the charge flows through a load, its energy decreases.
The electric potential energy (voltage) for each Coulomb of charge in a circuit is called the electric potential difference.

• The energy (needed to do work) = electric potential difference * charge or E = Q* V

• 1 Volt is  the electric potential difference between two points (if 1 joule of work is required to move 1 coulomb of charge between 2 points.



Resources:

     http://www.differencebetween.net/technology/difference-between-current-and-voltage/

     http://www.wordiq.com/definition/Potential_difference       
     http://www.educationalelectronicsusa.com/p/current_electricity-I.htm

Video:

You can aslo check the Video on Electric Circuits