Resistance
Conductors and insulators
Materials that allow an electric charge to flow through them are called conductors, while materials that do not allow the passage of electrical charge, are called insulators.
Electric current
An electric current is the flow of electric charge (electrons). A conductor is a material through which electrons(charges) can flow and are mostly metals. A metal (conductor) consists of particles that are called atoms. These electrons are not bound to any specific metal atom, and we say that the electrons in a metal (conductor) are free moving.
Electric current (2)
A metal (conductor) therefore consists of an arrangement of positive nuclei in a sea of free moving electrons. A conducting wire in an electrical circuit is made of metal. When the conducting wire is connected to a battery, the electrons move easily through the metal wire to produce an electric current- the electrons then all move together in the same direction through the wire to the positive termnial of the battery.
Conductor
Electrons are only held loosely by the positive nuclei.
Insulator
Electrons are held tightly by the positive nuclei.
Insulator
In an insulator(nonmetals) the electrons are being held tightly by the positive nuclei. As a result the electrons are not able to move freely, and no electrical current can flow when the insulator is connected to a battery. If you charge an insulator electrostatically by rubbing it with a piece of cloth, the charge remains on the surface of the insulator.
Insulator (2)
But the insulator slowly loses its charge into the air, especially in wet or moist weather. The charge is also quickly lost if you touch the insulator with your hand- this is known as the earth of the charge. One cannot charge a conductor by rubbing it. Any charge that is produced in the conductor flows through the conductor.
Resistance
There is no material that is perfect conductor. Although a conductor allows electrons (electric current) to flow through it, it does not always allow the charge to move through it unhindered. All conductors have a measure of resistance against the flow of electrons (electrical charge or current) that flows through it.
Resistance
Electrical resistance is the resistance offered y a conductor against the flow off current. A good conductor with a low resistance allows a strong current through while a conductor with a high resistance only allows a small current through. An electrical component that adds resistance to a circuit is a resistor.
Resistor
A resistor consists of a conductive material with a high resistance to control the current or for the provison of useful energy transfer, such as bulbs, rheostats, motors, light sensitive diode and light emitting diodes. When electrons (charge) move through the conductor, the electrons collide with the atoms that the conductor (metal) has been made of. When they collide, they transmit kinetic energy to the atoms and cause them to vibrate. The electrons therefore lose energy and move more slowly (energy is being wasted). In this way energy is converted into heat and light.
Factors that influence the resistance of conductors
Type of materials: Different conducting materials offer different forms of resistance against electrical current-copper wire conducts a greater cureent than an equal lenght of nichrome wire of the same thickness.
Lenght of the conductor: Longer wires offer more resistance than shorter wires.
Thickness of the conductor: Thinner wires offer more resistance than thicker wires.
Temperature of the conductor: Hotter conductors offer more resistance than colder conductors.