is electric field a function of time and space in a polarozed dielectric give reason why or why not
Answers
Answer:
Discussion
the basic idea
Dielectrics are insulators, plain and simple. The two words refer to the same class of materials, but are of different origin and are used preferentially in different contexts.
Since charges tend not to move easily in nonmetallic solids it's possible to have "islands" of charge in glass, ceramics, and plastics. The latin word for island is insula, which is the origin of the word insulator. In contrast, charges in metallic solids tend to move easily — as if someone or something was leading them. The latin prefix con or com means "with". A person you have bread with is a companion. (The latin word for bread is panis.) To take something with you on the road is to convey it. (The latin word for road is via.) The person you travel with who leads the way or provides safe passage is a conductor. (The latin word for leader is ductor.) A material that provides safe passage for electric charges is a conductor.
Inserting a layer of nonmetallic solid between the plates of a capacitor increases its capacitance. The greek prefix di or dia means "across". A line across the angles of a rectangle is a diagonal. (The greek word for angle is gonia — γωνία.) The measurement across a circle is a diameter. (The greek word for measure is metron — μέτρον.) The material placed across the plates of a capacitor like a little nonconducting bridge is a dielectric.
The plastic coating on an electrical cord is an insulator. The glass or ceramic plates used to support power lines and keep them from shorting out to the ground are insulators. Pretty much anytime a nonmetallic solid is used in an electrical device it's called an insulator. Perhaps the only time the word dielectric is used is in reference to the nonconducting layer of a capacitor.
Dielectrics in capacitors serve three purposes:
to keep the conducting plates from coming in contact, allowing for smaller plate separations and therefore higher capacitances;
to increase the effective capacitance by reducing the electric field strength, which means you get the same charge at a lower voltage; and
to reduce the possibility of shorting out by sparking (more formally known as dielectric breakdown) during operation at high voltage.
what's going on here
When a metal is placed in an electric field the free electrons flow against the field until they run out of conducting material. In no time at all, we'll have an excess electrons on one side and a deficit on the other. One side of the conductor has become negatively charged and the other positively charged. Release the field and the electrons on the negatively charged side now find themselves too close for comfort. Like charges repel and the electrons run away from each other as fast as they can until they're distributed uniformly throughout; one electron for every proton on average in the space surrounding every atom. A conducting electron in a metal is like a racing dog fenced in a pasture. They are free to roam around as much as they want and can run the entire length, width, and depth of the metal on a whim.
Life is much more restrictive for an electron in an insulator. By definition, charges in an insulator are not free to move. This is not the same thing as saying they can't move. An electron in an insulator is like a guard dog tied to a tree — free to move around, but within limits. Placing the electrons of an insulator in the presence of an electric field is like placing a tied dog in the presence of a mailman. The electrons will strain against the field as far as they can in much the same way that our hypothetical dog will strain against its leash as far as it can. Electrons on the atomic scale are more cloudlike than doglike, however. The electron is effectively spread out over the whole volume of an atom and isn't concentrated in any one location. A good atomic dog wouldn't be named Spot, I suppose.
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Explanation:
Since charges tend not to move easily in nonmetallic solids it's possible to have "islands" of charge in glass, ceramics, and plastics. The latin word for island is insula, which is the origin of the word insulator. In contrast, charges in metallic solids tend to move easily — as if someone or something was leading them. The latin prefix con or com means "with". A person you have bread with is a companion. (The latin word for bread is panis.) To take something with you on the road is to convey it. (The latin word for road is via.) The person you travel with who leads the way or provides safe passage is a conductor. (The latin word for leader is ductor.) A material that provides safe passage for electric charges is a conductor.