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### Course: Physics archive>Unit 11

Lesson 1: Charge and electric force (Coulomb's law)

# Conductors and insulators

A conductor is a material that allows electrons to flow freely through it, making it useful for carrying electric current. An insulatoris a material that resists the flow of electrons, so it does not allow electric current to pass through it. Learn about how conductors and insulators work and how they are effected by changes in electrical current. Created by David SantoPietro.

## Want to join the conversation?

• Isn't water one of the cases where it can be a conductor or an insulator?

I mean I have heard of ice batteries and stuff.
• Pure water (H2O) is not a conductor of electricity. A liquid can only conduct electricity if it has free ions because ions are the charge carriers there, there are no free electrons in water. However, because of the polar nature of the water molecule (moving into the realm of chemistry here), adding an acid or a base forms the ions required for conduction (H3O+ and OH- respectively). Alternately, you can add a salt, like NaCl, which dissociates into Na+ and Cl- ions. Then too, the solution will conduct electricity.
To sum up - pure water is a non-conductor, water with mobile ions is a conductor.

Oh and I Googled ice battery, it's just a device which forms ice at night (when the electricity rate is cheaper) so that it can cool the room during the day, thus saving costs.
• What is the difference between charge, electricity and energy. I really get confused. Thanks in advance.
• Charge is a property of an object (atom, molecule, person, etc), like mass. It tells how much force another charged object will apply on it. It is determined by the net amount of charged particles (protons and electrons) in the object.

Electricity is a broad term that used to mean a lot of things. Generally it refers to the flow of electrons.

Energy is the potential to do work (move) on another object. Moving objects have kinetic energy because if they hit another object, they would do work on that object. Charged objects can do work on other charged objects, so they have energy.
• Why the negative charge leave at ? Aren't them attracted by the positive charge in the rod?
• To repel from the other conductor's electrons
• Is there a name for the method David described first where he touched the conductor to the insulator?
• can we charge something negatively by conduction
• Yes. If you have a conductor A which is already negatively charged and you bring it in contact with another conductor B which is uncharged. Then B will acquire negative charge by conduction.
• Why are the electrons stuck in an insulator? Thanks in advance!
• Atoms that hold tightly to their electrons are insulators. Atoms that don't, aren't.
• if two insulating materials can interact with each-other and cause attraction like the balloon and the wall, why isn't every insulator attracted to another insulator? For instance should 2 plastic rods not attract each-other when moved close together?
• The reason for attraction between two conducting bodies is because of the charge. On e body has positive charge while the other attains negetive charge due to inducton. This charge is due to the free electrons in the body which are not present in insulators
• At ,David said that 'most' plastics are insulators . So ,Are there any plastics that can act as a conductor ?
• Materials engineers and chemists have found ways to make conductive plastics by altering regular plastics through some process. I'm not sure what this process is, or how they synthesize conductive plastics, but it is probably expensive and complicated. The process might involve "doping" which is used to make semiconductors, or it might involve treating the plastic with metal ions, to make it conductive.
But these are specialty chemicals that are too expensive to be commercialized (they only exist in labs perhaps); the most common plastics are thermoplastics (these include Nylon, Acrylic, and PLA) which can be molded into shapes and products.

I don't know much about plastics, but the topic seems very interesting, because plastics and semiconductor electronics often end up being toxic waste, and become harmful. Some scientists are using their knowledge of plastics, organic chemistry, and knowledge from the semiconductor industry to make "organic semiconductors", or essentially making electronics out of carbon-based materials instead of doped silicon. This would hopefully reduce toxic waste.