Motor Building

In the beginning, I was full of excitement to make our own motor with Edward. The process of making motor was easier than i expected. Rather than reading the instruction on workbook, we observed the motors that were made by previous students. For 30 minutes, we hammered four nails down and we took hard time to align the nails to adjust the right proportion. Then, we made the spinning part of the motor which was just a stick into a wine cork. Then, I sanded the brushes which will conduct electricity to the commutator. Commutators were attached on one side of the cork. We coiled the cork.

Right hand rule #1 (conductors)
     Thumb of right hand points in direction of conventional current flow, fingers point in direction of circular    magnetic field around conductor.

Right-hand rule #2 (coil)

 Curled fingers of right hand point in direction of conventional current flow, thumb points in direction of magnetic field around conductor.














http://outpost1.stellimare.com/scouting/mb/electricity/electromagnet.html

p.582~589 Magnetism and Electromagnetism

Key words:

domain theory of magnets: all large magnets are made up of many smaller and flexible magnets that can interact with each other.

dipoles: the small and flexible magnets that make up a large magnets.

electromagnet: a coil of wire around a soft iron core, which uses electric current to produce a magnetic field.

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

magnetic field: distribution of the magnetic force in the region of magnet

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

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

first right-hand rule for conductors:

right-hand rules:

second right hand rule for coils:
 3

Test compass: a compass used to check the presence of the magnetic field and to map a magnetic field.


Summary: 17.1 The magnetic Force-Another force at a Distance

• Similar magnetic poles, NORTH and NORTH or SOUTH and SOUTH repel each with a force at a distance.
• Dissimilar magnetic poles , NORTH and SOUTH, attract each with a force at a distance.
• Earth is a huge permanent magnet, producing own magnetic Field.
• Earth's magnetic field is produced by the flow of hot liquid metals inside Earth.
• All magnets are made up of iron, nickel, cobalt or mixture ( ferromagnetic metals)
• Magnetic materials are composed of smaller magnets which is based on domain theory of magnets.

                17.2 The Electromagnets

• Scientist developed hand signs to predict how magnetic forces act (right-hand rules)

p.553~563

16.5 Resistance- Ohm's law

The amount of current flowing through a resistor varies directly as the amount of potential difference applied across the resistor as long as other variables, such as temperature, are controlled. There is a resistance of 1 ohm when 1A of current flows with a potential difference of 1 V across a resistor.

Factors that determine resistance:

Resistance of a conductor depends on its length, cross-sectional area, the material made of, and its temperature.

Definition:

conservation of electric charge-  there is no net gain or loss of electric charge or energy.

conservation of energy- there is no net gain or loss of electric charge or energy.

gauge number- number on wire that indicates its cross-sectional area

resistance- a measure of the opposition to current flow

LAWS

Ohm's law- the ratio of V/I

Kirchhoff's current law-  the total amount of current into a junction point of a circuit equals the total current that flows out of the same junction.

Kirchhoff's voltage law- the total of all electrical potential decreases in any complete circuit loop is equal to any potential increase in that circuit loop.

 

Series Circuit
It =  I1 = I2 ....Vt= V1 + V2 ...
Rt= R1 + R2...

Parallel Circuit

Factors that affect Resistance

  

prelab Table

What is the diference between parallel and series circuit?

Defintion:

Seriers circuit:

-basic type of electrical circuit in which loads (components) are joined in a sequence so that the same current flows through all of them.

-In series circuits, the connection or circuit will not be complete if one component in the series burns out.

Parallel circuit:

-circuit in which loads are connected side by side

-the identical voltage occurs in all components, with the current dividing among the components based on their resistances.

-will still continue to operate, at least with other components, if one parallel-connected component burns out.

http://www.differencebetween.net/science/difference-between-series-and-parallel-circuits/

Q1~12 Circuit

Q1a. Can you make the energy ball work?

-Yes, my fingers and body worked as wires to complete the circuit.

Q1b. What make the ball falsh and hum?

-the completion of simple circuit by my body

Q2. Why do you have to touch both metals contacts to make the ball work?

-To make complete circuit, our fingers work as the wires and the switches

Q3. Will the ball light up if you connect the contacts with any materials?

-Yes, any conductors to electricity will light up the ball such as certain metals

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

- I tried pencils, pens(metal part), erasers, binder (metal part)... only some metals are conductors.

Q5. This ball does not work on certain individual what could cause this to happen?

-Individual who is not using bare hand such as wearing gloves, is not able to work the ball. Generally thinking,

every individual must work the ball since human can transfer electricity.

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

-Yes, two individuals touches on each contact of the ball, and other individuals connected their fingers or hands.

-Yes, it worked with the entire class perfectly.

Q7. What kind of a circuit can you form with one ball?

-Since, the ball works as every thing except the wires (including battery) , it is direct current.

Q8. Given 2 balls (combine 2 groups): Can you create a circuit where both balls light up? [1/3]

- Yes, I can create a circuit where both balls light up. Just how Q6 had been done, just by adding more

individuals(wires), it can be formed as parellel and series circuits.

Q9. What do you think will happen if one person lets go of another person's hand and why? [2/3]

- It depends on the circuit whether it is parellel or series circuit. In parellel circuit, disconnection of one wire will

not affect other side of connection. In series circuit, one disconnection will cause everything to be ruined.

Q10. Does it matter who lets go? Try it. [3/3]

- It depends on the type of the circuit. It will matter in the series circuit where the loads are connected one after

another. It does not matter in parellel circuit where one route disconnection will not affect another route since this

type of circuit is connected side by side


Q11. Can you create a circuit where only one ball lights (both balls must be included in the circuit)? [1/2]
-Yes, I can by using the method of parallel circuit. By just letting go of one route of circuit, another route will still

be working.

Q12. What is the minimum number of people required to complete this? [2/2]

-Minimum number of people to create parellel circuit is 3 people Since 6 wires can be created by 3

people.

What is the centre of gravity?

Centre of gravity:

Gravity acts downwards therefore the weight of any structure or any part of a structure acts vertically downwards. We assume that the whole weight of a structure acts through one point - the centre of gravity. The position of the centre of gravity will depend on the shape of the body.

 

The centre of gravity of an object does not necessarily have to be within a body, it can be an imaginary point in space.

The centre of gravity is very important in relation to stability. If a line through the centre of gravity falls within the structures base then it will remain stable.

If the line falls outside the structures base then there is a possibility that overturning will occur. This structure could be classified as unstable.

 

In order to make such a structure stable precautions would have to be taken. One example is where part of the structure is secured to the base and this prevents overturning occurring.

PHYSICS DAY 2

2nd PLACE :)
Objective: make the tallest and stable paper tower possible using limited sources
Unfortunately, our team was at 2nd place by just a few centimetres.

This activity was very exciting and i got to know more friends in the class. First, i recommended the method of rolling papers to make the high structure as possible. And Chung suggested to put the heavy bottom legs with walls surrounding the legs to make the structure stable. We could have made much taller structure if we did not waste too much newspapers at the bottom. Also, we should have thought about the mass of the news papers, so that we could roll different mass of papers and make the top the lightest. Overall, our structure was relatively well balanced compared to the small time we took and planned.

Physics of  our structure:

- Heavy bottom that supports the weight of the top
- Surrounding wall allowed the legs to be more stable
- As it goes to the top, we tried to make it the lightest as possible
- The thinkness or thiness determines the stability of the tower relative to the mass of top
- The center of the gravity

What make stable?:
- The heavy bottom and the wall
- The thicker legs then the top
- The center of the gravity allows the structure to be straight
-

1st Day- pg 544-552

Chapter 16


Definitions:

Alternating current(AC): current that continually changes direction

Ammeter:  a current measuring device

Circuit: the path of current

Direct current (DC): current that flows in a single direction from the power supply through conductor to a load and back to the power supply

Electric current: a flow of charge

Electric potential difference(V): the amount of work required per unit to move a positive charge from one point to another in the presence of an electric field

Electric potential energy: Energy stored when static electric charges are held a certain distance apart

Conventional current: the model of positive charge flow

Current: the total amount of charge moving past a point in a conductor, divided by the time taken.

Load: a device that converts electric enrgy to other forms of energy

parallel circuit: a circuit in which loads are connected side by side

voltmeter: an instrument for measuring potential differences in volts

Current:
I= Q/t  (I= current in amperes [A]) (Q=charge in coulombs[C]) (t=time taken)

Electric potential difference (voltage):
V=E/Q (E=energy required to increase the e.p of charge

Energy tranfered by charge flow:
E= VIt 

1C = 6.24 * 10^18  electrons

1e = 1.60 * 10^-19 C (Charge of one electron = 1/ 6.24 *10^18)

Equations: