Conductors are objects that readily let electrical current to go through.
Insulators are objects that resists heat/electricity/light/sound to go through (don't flow freely). Insulators' properties differentiate them from conductors and semi-conductors is that they have higher resistivity, like non-metals.
It isn't false that materials in the universe are categorized as insulators, electrical insulators or electrical conductors.
Semi-conductors/super conductors/other exotic forms of electrical materials exist, but most introductory physics classes, we get pretty far of it's either an insulating material electrically or conducting material electrically.
[1.1] Suppose 2 solid cylinders of either an insulating material or a conducting material.
Both insulators and conductors are made of a atoms and big number molecules.
Whether insulator/conductor, atoms and molecules are made of positive charge nucleus and a negative electron swarm around the nucleus.
Another similarity is that both conductors and insulators, positive charge nucleus can't move--can wiggle a bit by thermal vibrations, but can't move freely around.
A solid's positive charge nucleus are fixed.
What may move are negative electrons and the differences a conductor's some electrons can move freely, without much resistance, unlike insulators which has almost anything fixed without having the right energy levels and bands of electrons to move freely.
Fig 1
Electrons must be compelled to move with a battery/some an electric field/force. Then they migrate, but insulator's electrons are stuck.
It's somewhat true to to only care of conductors and insulators is only used if we don't want electrical interaction. But if we set its insulator up to a battery/set up some electric field/force here, no matter the electron in an insulator can't jump between atom, a nucleus and an electron cloud can move a bit.
Depending on an atom's polarity on a side (Fig 1), its nucleus moves to the atom's positive side from the negative side, which creates an overall electrical effect.
Thought charges of an insulator can't flow through an insulator, if all its atoms do this, it can react electrically.
If we add extra charges to the insulators/conductors, with the positives and negative same number, it gets messy.
If an insulator gets extra negative charges, they're stuck.
Note: Only extra charges are drawn.
If a conductor gets extra negative charges, they repel and move away from each as far away as possible (often to edges), probably even outside with enough energy.
Insulator materials:
glass
wood
plastic
Insulator materials:
gold
copper
silver
Good electrical insulators: air, cloth, rubber
Good thermal insulators: feathers, wool.
"2 rod" example
What happens if a conducting (metal) rod and rod with a negative net amount on the outside edge (what net charges do on conductors) touch?
Some charges go to the other rod to spread away as far as possible
If both rods are the same size, they have the same amount. If a rod is bigger, it gets more charge for them to spread more with some staying at their original rod.
Induction charging is a way to charge an object without actually touching to another charged object. Such process is when the charged particle is near an uncharged conductive material grounded on a neutrally charged material.
Charges separations An neutral object's electrons move away from the charged object, leaving the side closest to the charged object with a positive charge (deficit of electrons), creating polarization in the neutral object
Attraction The charged object attracts the neutra object's positive side, causing an attractive force between the 2 objects.
Grounding If the neutral object is grounded (connected to a metal pipe on ground/other big electron supply where we take infinite electrons without impacting the ground), electrons can leave the neutral object, making it positive charged.
We can cut the ground connection and remove what induced the charge, the neutral object retains its positive charge and charges that left can't return since the ground connection is cut.
Balloon and Hair: If we rub a balloon with hair, electrons go to the balloon, making it negatively charged. Bringing the balloon near a wall (an insulator), the wall becomes polarized, causing the balloon to stick to it.
If a metal cube with a negative charge -Q1 is in contact to a cylinder with a negative charge -Q2 where |Q1| > |Q2|, electrons move from the cube to the cylinder, as
A metal cube with positive charge +Q is in contact to an uncharged metal cylinder. Electrons move from the cylinder to the cube, since the cube is positively charged and electrons seek to get away as far from other electrons as possible.
If a metal cube and a metal cylinder both have the same positive charge +Q and are brought into contact to each other, no charge movement occurs since both are the amount and positive.
If a metal cube with a negative charge -2Q is in contact to a cylinder of a negative charge -Q, electrons move from the cube to cylinder, as
[Q1] Flashcard
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