Conductors and Insulators (1)

7/29/2019 Conductors and Insulators (1)

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Conductors and

insulators.


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Shocking!

If you reach for ametal doorknob afterwalking across acarpet, you might seea spark.

The spark is causedby electrons moving

from your hand to thedoorknob.


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Conductor!

A material in which electrons are able tomove easily is a conductor.

The best electrical conductors are metals.


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Not a Conductor!

A material in which electrons are not ableto move easily is an insulator.

Most plastics are insulators


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Charging Objects

Rubbing two materials together can resultin a transfer of electrons.

Then one material is left with a positivecharge and the other with an equalamount of negative charge.

The process of transferring charge by

touching or rubbing is called charging bycontact.


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INDUCTION!

Because electrical forces act at a distance,charged objects brought near a neutralobject will cause electrons to rearrange

their positions on the neutral object. The rearrangement of electrons on a

neutral object caused by a nearby charged

object is called charging by induction.


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Induction

The balloon on theleft is neutral. Theballoon on the right isnegatively charged. Itproduces a positivelycharged area on thesleeve by repellingelectrons.


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Detecting electric charge

When the device is notcharged, the leaves hangstraight down.

Notice the position of the

leaves on theelectroscope when theyare A uncharged, Bnegatively charged, andC positively charged


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Current and Potential

The net movement of electric charges in asingle direction is an electric current.

In a metal wire, or any material, electronsare in constant motion in all directions. Asa result, there is no net movement ofelectrons in one direction.


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Current and Voltage

When an electric current flows in the wire,electrons continue their randommovement, but they also drift in the

direction that the current flows. Electric current is measured in amperes.


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Voltage difference

In a similar way, electric charge flows from highervoltage to lower voltage.

A voltage difference is related to the force that causeselectric charges to flow. Voltage difference is measured

in volts.


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Electric Circuits

This figure shows anelectric current doingwork by lighting alightbulb.

A closed path that electriccurrent follows is acircuit.

If the circuit is broken by

removing the battery, orthe lightbulb, or one ofthe wires, current will notflow.


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Resistance

As the electrons flow throughthe filament in a lightbulb, theybump into the metal atoms thatmake up the filament.

In these collisions, some of the

electrical energy of theelectrons is converted intothermal energy.

Eventually, the metal filamentbecomes hot enough to glow,

producing radiant energy thatcan light up a dark room.


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Resistance

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Conductors and Insulators (1)