The right hand rule is able to help people determine which way the current is flowing in an electromagnet and predict the direction of electromagnetic force.
RHR #1 for conventional current flow
The person grabs the conductor using their right hand with their thumb pointing in the direction of positive current flow. The direction that the hand wraps around the conductor is the direction of the magnetic field.
RHR #2
The right hand grabs the coil so that the fingers and pointed in the direction of conventional current. The thumb points to the North end of the electromagnet.
Wednesday, September 22, 2010
Monday, September 20, 2010
Magnetic Force Pg. 582-589
-a magnetic field is the distribution of a force in the magnet
-there are two different magnetic characteristics, north and south
-similar magnetic poles will repel one another, and different poles attract
-a test compass is used to map a magnetic field
-the Earth acts like a magnet, it's magnetic field is produced because of the flow of hot liquid metals beneath the crust
-magnets does not only attract magnets, but they also attract metals that are not magnets, like iron, nickel, and cobalt, which are called ferromagnetic metals
-all magnets are made up of many smaller and rotating magnets, called dipoles, which can interact with other dipoles close by and when the dipoles line up, a magnetic domain is produced
-Oersted's Principle states that charge moving through a conductor produces a circular magnetic field around the conductor
-there are many right hand rules, the first one is where the right hand holds the conductor with the thumb pointing in the direction of positive current flow
-the second rule is when a coiled conductor is held in the right hand so that the curved fingers point in the direction of positive current flow, the thumb points in the direction of the magnetic field within the coil
-electromagnets have a strong magnetic field and produces a lot of magnetic force
-there are two different magnetic characteristics, north and south
-similar magnetic poles will repel one another, and different poles attract
-a test compass is used to map a magnetic field
-the Earth acts like a magnet, it's magnetic field is produced because of the flow of hot liquid metals beneath the crust
-magnets does not only attract magnets, but they also attract metals that are not magnets, like iron, nickel, and cobalt, which are called ferromagnetic metals
-all magnets are made up of many smaller and rotating magnets, called dipoles, which can interact with other dipoles close by and when the dipoles line up, a magnetic domain is produced
-Oersted's Principle states that charge moving through a conductor produces a circular magnetic field around the conductor
-there are many right hand rules, the first one is where the right hand holds the conductor with the thumb pointing in the direction of positive current flow
-the second rule is when a coiled conductor is held in the right hand so that the curved fingers point in the direction of positive current flow, the thumb points in the direction of the magnetic field within the coil
-electromagnets have a strong magnetic field and produces a lot of magnetic force
Tuesday, September 14, 2010
Resistance Ohm's Law
-The electrical resistance is the measure of the opposition to flow
-The resistance of an object can be calculated from dividing the voltage by the current
-The Greek letter Omega, Ω, is used to symbolize ohm
-There is a resistance of 1 ohm when 1 amp of current flows with a potential difference of 1 volt across a resistor.
-Every object has a resistance, the amount depends on the material's resistivity, the length of the material, and the cross sectional area
-The formula to calculate the resistance of a conductor is R=p(L/A). R is the resistance in ohms, p is the resistivity of the material in ohms x meters (calculated in lab results), L is the length of the material in meters, and A is the area of the cross sectional in m^2
-Conductors are able to become superconductors at very low temperatures, absolute zero which is 0 Kelvins equivalent to -273.15 degrees C
-To calculate the resistance within a series circuit, the resistance from all of the resistors is added together
-To calculate the overall resistance in a parallel circuit, 1 over the resistance of each resistor added together 1/Rt=1/R1+1/R2+1/R3+....+1/RN
-Three way light bulbs has two lights inside in a parallel circuit. It can light up one light, the other light, or both at the same time.
-The resistance of an object can be calculated from dividing the voltage by the current
-The Greek letter Omega, Ω, is used to symbolize ohm
-There is a resistance of 1 ohm when 1 amp of current flows with a potential difference of 1 volt across a resistor.
-Every object has a resistance, the amount depends on the material's resistivity, the length of the material, and the cross sectional area
-The formula to calculate the resistance of a conductor is R=p(L/A). R is the resistance in ohms, p is the resistivity of the material in ohms x meters (calculated in lab results), L is the length of the material in meters, and A is the area of the cross sectional in m^2
-Conductors are able to become superconductors at very low temperatures, absolute zero which is 0 Kelvins equivalent to -273.15 degrees C
-To calculate the resistance within a series circuit, the resistance from all of the resistors is added together
-To calculate the overall resistance in a parallel circuit, 1 over the resistance of each resistor added together 1/Rt=1/R1+1/R2+1/R3+....+1/RN
-Three way light bulbs has two lights inside in a parallel circuit. It can light up one light, the other light, or both at the same time.
Monday, September 13, 2010
Prelab Table
Name | Symbol | Unit | Definition |
Voltage | V | V | The energy that is lost between two points. |
Current | I | A | The flow of charge. |
Resistance | R | Ω | The measure of the opposition to flow. |
Power | P | W | Rate at which work is done. |
Friday, September 10, 2010
Circuits
Well, today in class, we were able to experiment with a special "ping-pong ball" that was able to light up and hum. I guess that within the ball there was a open circuit because it needed to be connected to work. The class separated into groups and needed to complete 12 challenging questions.
The Q & A's are below.
1. Can you make the energy ball work? What makes it flash and hum?
Everyone within the group were able to make the ball work by touching the 2 metal plates on the exterior of the ball at the same time. Human skin is a conductor similar to metal, so when we connected the circuit the current flowed from one of the contacts through our body into the other contact.
2. Why do you have to touch both of the metal contacts?
Both metal contacts need to be touched for it to work because the circuit needs to be closed/completed.
3. Will it light up if you connect it with any other material?
It will not light up with every material, only conductors and semi-conductors. The ball worked when I connected both contacts to a metal faucet, but it did not work when I connected them with plastic pens.
4. What materials will make the ball work?
Metals would be the best materials to make the ball work because they have free electrons to transfer the energy faster. The most conductive materials would include silver, copper, and gold.
5. This does not work on an individual. What causes this to happen?
For the toy ball to work, the individual needs to have moist skin. Withing that moisture, there are metals such as salts which contains electrons that can transfer the energy freely. If the skin is very dry, there will be less contact with the metal plates.
6. Can the ball work with 5-6 people or the entire class?
In our group, we created a circuit of 4 people with our fingers and one person touch one of the contacts and the other person touched the other. The ball lighted up and hummed.
7. What circuit can you form with the ball?
The circuit that we formed was circuit in series.
8. Can you create a circuit for 2 balls?
We created a circuit with 2 balls by combining two groups together. Both of the balled lighted up when the 4 people touched their fingers to the metal contacts.
9. What will happen if one person lets go of the other's hand? Why does it happen?
When one person let go of another person's hand the ball stopped flashing and humming. When they let go, the circuit changed from closed to open therefore creating an incomplete circuit.
10. Does it matter who lets go?
It does not matter who lets go because when one part is disconnected the entire circuit will stop working.
11. Can there be a circuit of two energy balls where only one ball lights up?
Yes, there can be a circuit of two energy balls where only one lights up. The circuit is called circuit in parallel.
This really bad drawing kind of shows how to make one out of two balls light up within a circuit. The objects are on both sides of the parallel circuit. They both have power supplies. The resistors are placed right before the batteries, making the balls work only after the electric current flows through the circuit. In the diagram, the circuit is disconnected on the left top side stopping the current of the left ball, but on the right side, the circuit is still connected.
12. What's the least number of people for this to work?
I think that the least number of people needed for this to work is actually 1. Each hand touches 1 contact on each ball, this would create a parallel circuit. When a finger is removed from one circuit, the other one would still work by passing the electric current through the body and into the other hand.
*Additional*
The question isn't really that specific. After thinking about it a bit more, the least amount of people needed for this to work is none because, we could just connect 3 metal wires to the ball for it to work. Two connecting one contact from each ball and one in the middle that connects the wires to make it a parallel circuit.
The Q & A's are below.
1. Can you make the energy ball work? What makes it flash and hum?
Everyone within the group were able to make the ball work by touching the 2 metal plates on the exterior of the ball at the same time. Human skin is a conductor similar to metal, so when we connected the circuit the current flowed from one of the contacts through our body into the other contact.
2. Why do you have to touch both of the metal contacts?
Both metal contacts need to be touched for it to work because the circuit needs to be closed/completed.
3. Will it light up if you connect it with any other material?
It will not light up with every material, only conductors and semi-conductors. The ball worked when I connected both contacts to a metal faucet, but it did not work when I connected them with plastic pens.
4. What materials will make the ball work?
Metals would be the best materials to make the ball work because they have free electrons to transfer the energy faster. The most conductive materials would include silver, copper, and gold.
5. This does not work on an individual. What causes this to happen?
For the toy ball to work, the individual needs to have moist skin. Withing that moisture, there are metals such as salts which contains electrons that can transfer the energy freely. If the skin is very dry, there will be less contact with the metal plates.
6. Can the ball work with 5-6 people or the entire class?
In our group, we created a circuit of 4 people with our fingers and one person touch one of the contacts and the other person touched the other. The ball lighted up and hummed.
7. What circuit can you form with the ball?
The circuit that we formed was circuit in series.
8. Can you create a circuit for 2 balls?
We created a circuit with 2 balls by combining two groups together. Both of the balled lighted up when the 4 people touched their fingers to the metal contacts.
9. What will happen if one person lets go of the other's hand? Why does it happen?
When one person let go of another person's hand the ball stopped flashing and humming. When they let go, the circuit changed from closed to open therefore creating an incomplete circuit.
10. Does it matter who lets go?
It does not matter who lets go because when one part is disconnected the entire circuit will stop working.
11. Can there be a circuit of two energy balls where only one ball lights up?
Yes, there can be a circuit of two energy balls where only one lights up. The circuit is called circuit in parallel.
This really bad drawing kind of shows how to make one out of two balls light up within a circuit. The objects are on both sides of the parallel circuit. They both have power supplies. The resistors are placed right before the batteries, making the balls work only after the electric current flows through the circuit. In the diagram, the circuit is disconnected on the left top side stopping the current of the left ball, but on the right side, the circuit is still connected.
12. What's the least number of people for this to work?
I think that the least number of people needed for this to work is actually 1. Each hand touches 1 contact on each ball, this would create a parallel circuit. When a finger is removed from one circuit, the other one would still work by passing the electric current through the body and into the other hand.
*Additional*
The question isn't really that specific. After thinking about it a bit more, the least amount of people needed for this to work is none because, we could just connect 3 metal wires to the ball for it to work. Two connecting one contact from each ball and one in the middle that connects the wires to make it a parallel circuit.
Series and Parallel
In a series circuit, the loads (eg. light bulbs) are connected in a single path. When a part of the circuit is disconnected, the entire connection cease to work. A great example of circuit in series would be Christmas lighting, they are connected one after the other.
In a parallel circuit, there are more than one resistor and multiple parallel paths for charges to move through. These are placed side by side, so if one of the loads in the circuit is broken, the charge will stop moving through that path, but continue to pass through the others. This type of circuit is used everywhere. When somebody turns off the television, it wouldn't turn off all of the electricity in the house.
Thursday, September 9, 2010
Physics of Tall Structures
Yesterday, in Physics class, the activity was to build the tallest structure out of newspaper and some tape. My group members came up with the idea of crumpling up paper to make a "small" base and thought that it would actually support the weight of the entire building.It was one of the most ridiculous designs ever. In the end, as I expected, the center of gravity for the structure was too high and the height needed to be shortened so it doesn't fall over by itself. Our's was the shortest.
The best building design would be to make a triangular/rectangular pyramid at the bottom with rolled up newspaper (as other groups did). After that, roll around 2-3 full pages and tape one on top of the other. The base should be able to sustain the weight of the structure still. Above that, the newspaper needs to be ripped/cut into smaller pieces which would be made into prisms, (triangular or rectangular and simple). A full page of newspaper could create a length of maybe 2 meters, saving materials and making the top very light. The reset of the paper can be user to add supports to the base. This would make the center of gravity very low therefore it wouldn't topple over that easily.
The best building design would be to make a triangular/rectangular pyramid at the bottom with rolled up newspaper (as other groups did). After that, roll around 2-3 full pages and tape one on top of the other. The base should be able to sustain the weight of the structure still. Above that, the newspaper needs to be ripped/cut into smaller pieces which would be made into prisms, (triangular or rectangular and simple). A full page of newspaper could create a length of maybe 2 meters, saving materials and making the top very light. The reset of the paper can be user to add supports to the base. This would make the center of gravity very low therefore it wouldn't topple over that easily.
Wednesday, September 8, 2010
Current Electricity Notes
Notes on Pg. 544-552
- Electric current involves electrons repelling one another and passing through a conductor
- The flow of charge is called electric current
- One ampere is one coulomb of charge moving through a point in a conductor every second
- Current is a flow of negatively charged electrons repelling one another, so current moves from negative to positive
- An ammeter is a device that measures the current
- In direct current, the current flows in a single direction from the power supply
- In alternating current, the current flow reverses often
- The path of a circuit is called a current
- Potential difference between two points in a circuit can be measured using a voltmeter
- The electrical potential energy for each coulomb of charge in a circuit is called the electric potential difference
Formulas
Electric Current
Name Symbol SI Unit
Current I A (amperes)
Quantity of Charge Q C (coulombs)
Time t s (seconds)
1 A=1 C/1 second
It is the rate of electric charge flow over a period of time.
1 A=1 C/1 second
It is the rate of electric charge flow over a period of time.
Name Symbol SI Unit
Electric Potential Difference V V (volts)
Electric Potential Energy W or E J (joules)
Quantity of Charge Q C (coulombs)
1 V=1 J/1 C
1 V=1 J/1 C
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