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Each day readers send in questions and feedback concerning the various lessons in the School for Champions website. A total of 15496 letters have been answered.



List of most recent 15 letters

Title

Subject

Section

Country

Isn't 60hz better for AC electricity? Electricity USA
 
Why is oxygen classified as non-polar? Chemistry Namibia
 
Using a refrigerator in Pakistan Electricity Pakistan
 
Definition of force at a distance Physics USA
 
Practical application of static electricity Static Electricity Ghana
 
Understanding temperature limits equation Physics Thermal Energy Brazil
 
Can understand maths but not science Physics SA
 
Current difference at different AC frequencies Electricity South Africa
 
Using a capacitor to start a DC motor Electricity India
 
Resource Vitality USA
 
I can see into the future Senses New Zealand
 
I enjoy your lessons Thanks South Africa
 
Want to become a more knowledgeable person. Knowledge UK
 
Decrease in potential energy from falling water Gravity Botswana
 
Can predict earthquakes, but people laugh Senses USA
 

Next 15 letters


Isn't 60hz better for AC electricity?

Electricity

June 27, 2016

Question

Is there no significance to the fact that there are 60 seconds in a minute, etc, etc?
Does not 60 hertz fit nicely with clocks and many other devices?

Tom - USA (27109)

Answer

The relationship between time and 60hz seems to make sense. When Nikola Tesla devised a system for AC electricity he had calculated that 60Hz was the most effective frequency. However, the German company AEG started generating electricity and decided to use 50Hz to better fit their metric standards. Thus much of the world uses the less efficient 50hz.

See Background of Worldwide AC Voltages and Frequencies.

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Why is oxygen classified as non-polar?

Chemistry

June 25, 2016

Question

why oxgyen is classfied as non polar and carbon dioxide polar ?

Johannes - Namibia (27105)

Answer

Whether a molecule is polar or non-polar depends on its geometry. Oxygen exists as a molecule of two oxygen atoms. The combination balances the distribution of their electrons.

Carbon dioxide is also a non-polar gas for the same reason.

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Using a refrigerator in Pakistan

Electricity

June 19, 2016

Question

I have Refrigerator 220 v 60h can I use in Pakistan? because I want to transfer this item to my own country.

Mohammad - Pakistan (27094)

Answer

Some refrigerators can use either 60 hz or 50 hz. You should check with the manufacturer--perhaps on their website.

Otherwise, it probably will still run on 50 hz, but it would not be as efficient.

The voltage difference doesn't matter, because it is an average.

I hope that helps.

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Definition of force at a distance

Physics

June 18, 2016

Question

definition of force at a distance?

- USA (27090)

Answer

Most forces require direct contact, but there are some forces that act when the object are separated--even at great distances. A good example is gravitation, where there is a pull from very great distances. Magnetism is also a force at a distance, since the magnets act on each other when separated.

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Practical application of static electricity

Static Electricity

June 17, 2016

Question

some practical application of static electricity

abdulrazaq - Ghana (27087)

Answer

You can use static electricity as a tool for dust removal in the air. Also, some dusting brooms used in the home employ static electricity to collect dust from the furniture.

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Understanding temperature limits equation

Physics

June 16, 2016

Question

Hi,

I need to know about it 3mc² / 2k, I want to complete it. where I study?

DOUGLAS - Brazil (27083)

Answer

The temperature of an idea gas is related to velocity: T = 3mv²/4k. When the velocity of the particles approach the speed of light, the equation changes to T = 3mv²/4k. (See Equations for Temperature Limits). Details can be seen at Kinetic Temperature.

But note that there are several other theories related to the maximum temperature, including the Theory of Relativity.

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Can understand maths but not science

Physics

June 16, 2016

Question

Good day
I would be happy to know what makes me to understand maths clearly and not to understand physical science concepts? well I do not understand anything since the beginning of the year of my grade 12 but now I would love to change and I'm asking for help so I can make it this year with distinctions in this subject.

kgomotso - SA (27084)

Answer

Mathematics is fairly abstract. so you must have more ability in dealing with numbers and abstract concepts.

On other other hand, Physical Science primarily concerns real objects and their properties. Observation of objects around you and how they behave under different circumstances is valuable in understanding the various science concepts.

Advanced Physical Science starts becoming more and more mathematical, where formulas and equations are used to describe and predict how object behave. If you are good in the maths, you should have an advantage on others in Physical Science.

I hope that helps. Best wishes in excelling in Physical Science. I am sure you will.

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Current difference at different AC frequencies

Electricity

June 15, 2016

Question

Good day.

Good articles on your page. What would the amp current difference be between say a 315 kW 50 Hz motor running on 525 volt compared to same motor running on 60Hz at 525 volt

Johann - South Africa (27080)

Answer

Assuming there is no other devices, such as inductors and capacitors in the circuit, the current or amps would not be affected by the frequency. There would be no difference.

Current = Power/Voltage. Thus I = 315 kW/525 V.

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Using a capacitor to start a DC motor

Electricity

June 14, 2016

Question

For starting any motor, initial torque has to be overcome. If one wants to start a DC motor of sufficient horse power, say 0.5 HP or more, a solar panel will not be able to give sufficient amperage. Will it be possible to start such a motor with sufficient Solar PV Panels, but low current, connected to a capacitor ? If so, the connection should be in series or in parallel ? Can you elucidate ?

Gadepalli - India (27077)

Answer

Overcoming the torque required to start a motor can be a problem. One possibility is to have an auxiliary battery used only to help start the motor. A capacitor is another possibility, provided to can recharge the capacitor during normal operations.

Since a capacitor is essentially an open circuit, I believe it would have to be placed in parallel to your motor circuit.

I hope that helps.

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Resource

Vitality

June 13, 2016

Question

Hi,

I spent longer than I intended browsing through the resources on your site (specifically, this page: http://www.school-for-champions.com/vitality/resources.htm) and found several I'd not seen before. I can only imagine the help and support you've given those seeking information on taking care of all aspects of their health, not just one side of it!

My team and I recently completed a new article, which I'm passing along to you for consideration: http://www.drugrehab.org/the-45-warning-signs-of-prescription-drug-abuse/

It discusses the critical warning signs that a loved one may be abusing their prescription drugs.

If you feel it meets your requirements, we'd be honored to have you include it on this resource page. If you don't, we'd love to know that too so that we can make changes to the piece to ensure it's the most valuable resource it can be.

Keep up the great work -- you’ve really inspired me!

Best,
Elizabeth

Elizabeth - USA (27076)

Answer

Thanks for article resource. I added a link to it at Health Resources - Drug Dangers.

Best wishes with your efforts.

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I can see into the future

Senses

June 12, 2016

Question

I can see into the future for about an hour but it's been nearly 2 years seens and felt my 10 sense but now I'm always in my 6th or 1 sence.I just have to show you how to change your thoughts in the future by understanding what time when u hear or think or say in your head or mouth. Ivan show you if I'm in the same room small

Rakesh - New Zealand (27073)

Answer

You have sensitive senses to be able to foresee future events. However, being able to affect or change the thoughts of another person is not really a sense. It is uncertain if this is some sort of force at a distance.

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I enjoy your lessons

Thanks

June 12, 2016

Question

I enjoy your lessons and Im able to understand to solve equations. I find this very helpful.

Xihluke - South Africa (27074)

Answer

I am glad that the material has been useful to you. Best wishes for success in your studies. I know you are the type of person who will be a champion.

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Want to become a more knowledgeable person.

Knowledge

June 12, 2016

Question

i would like to become a more knowledgeable person.

kelly - UK (27075)

Answer

Wanting to be more knowledgeable gives you a head-start over the average person.

Being curious and observant are important in gaining knowledge. Consider things you are interested in and study and read about them until you become well-versed in the subject. This can lead to other areas of interest.

Reading is the best way to be more knowledgeable. But it is also good to be able to express your knowledge and apply it.

I hope these ideas help. Best wishes in becoming a more knowledgeable person. I am sure you will succeed.

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Decrease in potential energy from falling water

Gravity

June 11, 2016

Question

On leaving the dam,the water falls through a height of 15 m. (G=10 N/kg).calculate the decrease in the potential energy of 500 kg of water falling from the dam to the turbine.

Lukoji - Botswana (27071)

Answer

PE = mgh. At the top of the dam, m = 500 kg, g = 10 N/kg, and h = 15 m. Thus the PE = 500 * 9.8 * 15 = 75,000 N-m.

At the turbine, PE = 0 and all the energy is then kinetic energy. The decrease in PE is 75,000 N-m.

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Can predict earthquakes, but people laugh

Senses

June 10, 2016

Question

Hello, my name id Debbie. I don't like to talk about this because of the negative feedback I get from some people. I always seem to know when there is going to be an earthquake, usually the day of or before, up to two weeks in advance. I'd say 90% have come true. Of course, I live in Southern California. Maybe my body is just tuned into it, not sure, the "Feeling" I get is one of unbalance with the earth and myself. It's very difficult to explain. I told my husband yesterday morning that an earthquake was coming, he just laughed! Sure enough, we had a 5.2 magnitude quake in Borrego Springs, about 100 miles from where we live at 1:04 am. I jumped out of bed! Someone once told me that my thrid eye was really open (whatever that means)But, It might have something to do with it? I just feel the earth is "off" some how, that something isn't right and then my prediction usually comes true, Something about the magnetic pull of the earth, I guess? Thanks for reading, Debbi

Deborah - USA (27068)

Answer

For many years, the Chinese have used barnyard animals to predict when earthquakes will occur. See The Use Of Animals In Earthquake Prediction and Can Animals Sense Earthquakes?.

So, it is possible that you are able to sense the subtle vibrations and tension in the air that may come before an earthquake occurs.

If you are also able to sense or predict other future events, you could have a strong precognition 6th sense. Most people have that sense to a small degree.

Whatever the case, don't let others get you down, because of your ability. For some people, it is probably not worth telling them.

Best wishes with your predictions. But I hope you won't have to predict any bad earthquakes.

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