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Answers to Readers' Questions on Physical Science:

Electrical Charges

The following 31 comments and questions have been sent in. They are listed according to date.

List of first 10 items

• Why is repulsion used to examine charges?
• What is quantum theory?
• Why can't we see electrons?
• What particles have a positive charge?
• Can like charges ever attract each other?
• Can electrical curent be sent through a laser?
• Experiment with magnets and temperature
• Why do things stick together?
• Is electric field intensity a vector quantity?
• Static electricity experiment

Next 10

Why is repulsion used to examine charges?

Question

November 8, 2009

why is repulsion considered as the surer test for having charge on a body?

tapash - India

18632

Answer

If you have two light weight objects on a string, such as pith balls or small balls of tissue, giving them both the same charge will cause them to separate and stay separated for a while. You can even measure the separation.

But if they have the opposite charge, they come together, so you can't really tell how much charge there is. Also, they may exchange charges, such that they both have similar charges. What happens then is that they come together and then separate slightly.

Thus, repulsion is a more accurate way to examine charges.

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What is quantum theory?

Question

September 18, 2008

what is quantum theory? explain it.

rupesh - India

16518

Answer

When you get to distances at the atomic level or smaller, motion is not smooth and continuous. Instead it is in quantum jumps. There are other unusual properties of matter that are not the same as in larger scales. One thing is that particles of matter--such as an electron--act both as a particle and as a wave.

Much of Quantum Theory has been verified by experiments.

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Why can't we see electrons?

Question

July 9, 2008

Why can't we see electrons? I know it is invisible, but why?

Elect Barizomdu - Canada

16199

Answer

Electrons are extremely small. There are microscopes that can barely see a single atom. But the electron is many times smaller than an atom. But the electron is not invisible.

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What particles have a positive charge?

Question

May 15, 2008

i dont really get it. i want more help. what particle(s) have a positive charge?

faida - USA

15959

Answer

Electrons have a negative charge. Protons have a positive charge. An atom with an extra electron is a negative ion. An atom that is missing an electron is a positive ion.

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Can like charges ever attract each other?

Question

April 1, 2008

can like charges ever attract each other???

pragati - India

15641

Answer

No. Their properties state that like charges always repel each other.

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Can electrical curent be sent through a laser?

Question

December 29, 2007

can electrical curant be sent through a laser and if so how much?

Patrick - USA

15036

Answer

Some lasers are started by sending an electrical current through the material. But also, you can send an electrical current though the laser, because the material is often ionized.

The amount of current depends on the type of materials in the laser. There should be no real limit.

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Experiment with magnets and temperature

Question

November 7, 2007

Hi. My name is Logan, and I'm in 7th grade. The Science Fair is coming up, and I'm thinking of doing something with magnets. Do you know if the power of an electric charge is affected by the temperature it's in?

Logan - USA

14737

Answer

A magnet can lose its strength when it is heated. A hot wire has more electrical resistance than a cool wire.

You could make a simple electromagnet from a nail, wire and battery and see whether its strength changes with temperature. Note that thin wires warm up more than thick wires when a current runs through them. Also note that keeping the electromagnet on for too long will quickly wear out the battery.

I hope these ideas help you in your project.

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Why do things stick together?

Question

June 30, 2007

why in static electricity things stick together not because of one made of matter & other is made of anti matter???

perihan - Egypt

14004

Answer

When some materials rub together, one collects negative electric charges on its surfaces and the other collects positive charges on its surface. Opposite electrical charges attract, thus causing materials to stick together.

Anti-matter consist of atoms or particles that are completely opposite the normal matter we see. When matter and anti-matter come together, there is usually an explosion.

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Is electric field intensity a vector quantity?

Question

April 26, 2007

Sir is electric field intensity vector quantity? or is it just the magnitude of electric field?and sir wut is the difference between electric field intensiry and electric field?

Sir could u also tell me the difference between COULOUMBIC forces and ELECTRIC forces

Ayush - India

13650

Answer

An electrical field is a force that an electrical charge exerts on other objects. By convention, it is a vector in the direction away from a positive charge.

The intensity of the electric field is the strength of the field. The square of the intensity is the electrical density.

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Static electricity experiment

Question

February 11, 2007

can you make an explaination for this situation: A charge rod is brought near a pile of tiny plastic spheres.Some of the spheres are attracted to the rod but as soon as they touch the rod, they fly away in different direction.Explain

jhehan - Philippines

13125

Answer

This is studied under static electricity. A charged rod will attract neutral tiny plastic spheres. Once the spheres touched the rod they gain the same charge as the rod. Like electrical charges repel, and the spheres shoot away from the rod.

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