Building The Motor

Few days ago, our physics class had an exercise where we tried to build our own basic motor. Our understanding of electromagnetism at the time to me, wasn’t at its fullest, so this simple exercise was a great opportunity for us to learn in a more practical way.  We were asked to bring our own materials, such as nails, wood base and the cork. I was really wondering if John and I’s motor was going to work. Even though the “ingredient” to success was printed right in the book, but I was just not sure that we understand the concept enough to apply it to real life.
But anyways, the exercise continued, I mean it was still a good learning experience whether we succeed or not. First we had to nail 4 long needles in pairs of 2, 2 to 3 cm apart. This was to hold the magnet, to create that interaction of magnetic fields. Then we nailed in few smaller ones in between the 4 big nails, this was to hold the cork so there’s space for it to rotate. After we’ve secured the base of the motor, we moved on to the cork. First we used a long stick and threaded it inside the cork, it was then held by the 2 holders we built before. Then we focused on the cork – motor itself. We first put the commuter pins in the front side of the cork, they were an important for ensuring the current reversal. Then we wrapped the wire parallel to the pins, and attached each end of the wires to the pins. This would create the interaction between magnetic field once current runs through the wire. The last part – which was also the hardest, was to make sure that the brushes touched the pins perfectly. We had a lot of trouble there because the brushes weren’t always at their greatest location, and it would always collapse after few rotate. However, after some struggles, we finally set it at a good place, where it would ensure the continual rotation of the motor. And Voila! Our motor is complete. Well it wasn’t the greatest motor built from wood and cork, but it worked on its second try, stubbornly ;)

The thumb will point to the direction of the current, and the curled fingers show the direction of rotation of the magnetic field

RHR #2 is based on Rule #1 because in a coil, it consists of many circular magnetic field in both directions. In addition, the force of the sum of all these magnetic fields result of a much bigger magnetic field as shown above

Electromagnetism

Magnetic Force
Magnetic Field – A distribution of a magnetic force in the region of a magnet.
Law of magnetic forces: Opposite Attracts / Same Repels

North attracts to South and repels North, vice versa

A good way to show magnetic field is to spread iron fillings near a magnet. 

Earth itself is an enormous magnetic field, produced by the flow of lava in the core.
Compasses always point to the north because it is attracted by the Earth’s magnetic field. However, we know that opposites attract, thus the Geographical North Pole is known as the physical/magnetic south, and vice versa.
 

Domain Theory of magnets: All large magnets are made up of many smaller magnets, called dipoles. Their magnetic force is only “activated” or in full power when all domains are lined up. 

Electromagnets:
In earlier days, magnetism and electrostatics were not considered the same field of study.  Thus, people did not know how to apply magnetism in the field of electrostatics, which is essential for many technologies today.
However, scientists have broken the barrier between magnetism and electrostatics, namely Gilbert and Oersted.
 

Oersted’s Principle: Charge moving through a conductor produces a circular magnetic field around the conductor.
 

(Both follow conventional current flow)
Right Hand Rule #1: 

 
Right Hand Rule #2:

 

Electromagnet Factors
·    Current B2 = B1(I2/I1)
·    Number of turns in the coil B2 = B1(n2/n1)
·    Type of Material
·    Size

Notes 553-563

Volt (The amount of push) and the nature of pathway (conductivity) determine the amount of current flow.

Opposition of flow – Resistance means the pathways of the circuit are more difficult to flow.

Equation: R(Ω) = V(V)/I(A)

R: Resistance, measured in ohm (Ω)

V: Voltage, measured in volt (V)

I: Current, measured in amperes (A)

The ratio of V/I is called Ohm’s law (George Simon Ohm), and it is constant.

 

Conductor’s Resistance depends on:

Length	Longer: More resistance	R1/R2=L1/L2
Cross-sectional area	Larger Cross sectional area: Less resistance	R1/R2=A2/A1
Type of Material	Higher Ressistivity (Ω*m): More resistance	R1/R2=p1/p2
Temperature	Higher Temperature: More resistance	Not for all substances

Example of calculating resistance:

R1/R2=L1/L2

R2=R1(L2/L1)

R2=1.7 Ω(50m/200m)=0.42 Ω

Superconductivity: Ability of a conductor conducting electricity without heat loss due to resistance.

Highest temperature superconducting materials, HTS, can reach the temperature of 140K (-133°C)

Series and Parallel Circuit

Kirchhoff’s current law: The total amount o f current into a junction point of a circuit equals the toal 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.

Kirchhoff’s laws prove that in any circuit, there is no net gain or loss of energy.

(Because of conservation of electric charge and the conservation of energy)

 Resistances in a Series Circuit

·    A single path way

·    Current through each resistor is the same

·    Sum of all potential energy loss through each resistor is equal to the total voltage

From Kirchhoff’s law, We know that 

 From Ohm’s law R=V/I, We get

Resistances in a Parallel Circuit

·    More than 1 pathway

·    Voltage is the same through each resistor

·    Sum of the currents flowing into a junction point is equal to the amount of currents flowing out of the same junction.

From Kirchhoff’s law, we know that

From Ohm’s law R=V/I, We get

Chart

Name	Symbol	Unit	Definition
Voltage	V	V	The electric potential energy for each coulomb of charge in a circuit
Current	I	A	The rate of flow of charge.
Resistance	R	Ω	A measure of opposition to current flow.
Power	P	W	The rate of which work is done.

What is the difference between a parallel circuit and a series circuit?
 

Series Circuit:
 

• Has only a single path between two points
• In other words, every component of the circuit above (battery, switch, ammeter, load) are all in “series” with each other.
• Therefore, all loads in a closed series circuit are controlled by only 1 switch, the status of all loads must be either on or off at the same time.

Parallel Circuit

• Has several paths connected side by side between two points, each parallel path is called a branch in a parallel circuit
• The current splits up and flow through different paths and delivers energy to all loads, then joins together again.
• Therefore, there are multiple switches in a parallel circuit that controls each load as they’re in different paths of the circuit.
• The voltmeter must be in parallel in a circuit.

Energy Ball

1.Can you make the energy ball work? What do you think makes the ball flash & hum?

Yes, the energy ball would flash and hum whenever I place a finger on each of the two iron contacts on the surface of the ball. This is because by placing my fingers on the iron contacts, I’m actually closing and connecting the circuit to allow energy to transfer. That is, the current flow is actually being transferred through my own body.

2. Why do you have to touch both metal contacts to make the ball work?

It is necessary to touch both metal contacts because they’re like the terminals of the circuit. Current electricity could not flow continuously without two terminals.

3. Will the ball light up if you connect the contacts with any material?

No, because in order to allow electricity to flow, we must have conductors that can transfer the current in the circuit. Therefore, any non electricity conductive materials will not make the ball light up.

4. Which materials will make the energy ball work? Test your hypothesis

In theory, any material that is a conductor of electricity will make the energy ball work, such as lead and steel (metals); and water. In our group, we first tested the hypothesis with materials such as pencil lead and the cable (of course and ourselves), and the ball worked fine. But when we tried materials such as plastic pencil and cloths, the ball did not hum and flash. This proves that our hypothesis was correct: Only materials that are conductors of electricity can make the ball work.

5. This ball does not work on certain individual.  What could cause this to happen?

To say that the ball would not work on certain individual is nearly impossible; it’s like saying that the individual does not contain any water in his/her body. The only possible cause to this occurrence is when the passage of current flow is obstructed, such as covering your fingers with cloth or wearing a rubber glove.

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

If we as a group form a circle (series circuit), the ball would work even when the circuit is bigger. Following this theory, it will work with the entire class also because the amount of people would only increase the size of the circuit, but not how it functions.

7. What kind of a circuit can you form with one energy ball?

With one energy ball, I can form a series circuit because in order to form a parallel circuit, we must have at least two balls parallel to each other.

8. Given two balls: Can you create a circuit where both balls light up?

Yes and as a matter of fact, we can create either a parallel or series circuit with two balls. The idea of it is still the same (which is to create a closed circuit with everybody holding hands), except with more people and an addition ball, we can form bigger and more complex circuit.

9. What do you think will happen if one person lets go of the other person’s hand and why?

The energy ball would stop working if one person lets go because it would disconnect the circuit and form an opened circuit. In a series circuit, both balls would stop working because the circuit is connected in a single path. Thus, when one person ruins the completeness of the circuit, the flow of electricity would completely stop. However, in a parallel circuit, it would matter because the energy balls are side by side independently. Thus, disconnecting one link would only stop from working while the other one would still be flashing.

10. Does it matter who let’s go? Try it.

As mentioned in question 9, it would matter for a parallel circuit because the circuit has two or more paths.  Thus, one disconnection would only stop the current flow in one of the two paths. In addition, where the disconnection occurs will also determine which path would be disconnected, therefore which energy ball that would stop working. For example, if we treat the parallel circuit as two quadrilaterals, if the disconnection occurs in the top quadrilateral path, then the energy ball connected in the top square would stop working. Vice versa, the same phenomenon would occur for the bottom quadrilateral.

11. Can you create a circuit where only one ball lights (both balls must be included in the circuit)?

Yes it’s possible because we can use a parallel series with a switch. By turning off the switch of one of the path way, it would stop the current flow of one energy ball, while its parallel circuit would still be working.

12. What is the minimum number of people required to complete this?

The minimum number of people required to complete this is 3 people.