3. conductors and insulators.pdf

Conductors and Insulators Conductors are made of materials that electricity can flow through easily. These materials are made up of atoms whose electrons can move away freely.  Metals in general are the best conductors of electricity. The atoms of metal elements are characterized...

Conductors and Insulators Conductors are made of materials that electricity can flow through easily. These materials are made up of atoms whose electrons can move away freely.  Metals in general are the best conductors of electricity. The atoms of metal elements are characterized by the presence of electrons in the outer shell of an atom that are free to move about. It is these ‘free electrons’ that allow metals to conduct electric current. Many metals like copper, iron, silver etc. are good conductors of electricity.  Silver is the most conductive metal, however it is very expensive and hence is rarely used. All the electric wires are generally made from copper. Some examples of conductors are: COPPER ALUMINUM PLATINUM GOLD SILVER WATER PEOPLE AND ANIMALS TREES Superconductor: A superconductor is a material that is a perfect conductor. Superconductors are usually a mix of two or more metals. Superconductor: However these are not superconductors at room temperature. They show zero resistance to electric flow at very low temperature usually below -200 degrees celsius. Insulators are materials opposite of conductors. The atoms are not easily freed and are stable, preventing or blocking the flow of electricity.  In insulators the outer electrons are tightly held together, which prevents them from moving. When the movement of electrons is restricted, no current can flow through them. Non-metals such as glass, wood, plastic are excellent insulators as they have high resistance to the flow of electric current.  This is true for normal voltage but increase in voltage may conduct some passage for electricity. Insulating materials like plastic, wood etc are used to cover materials that carry electricity. Some examples of insulators are: GLASS PORCELAIM PLASTIC RUBBER Electricity will always take the shortest path to the ground. Your body is 60% water and that makes you a good conductor of electricity. If a power line has fallen on a tree and you touch the tree you become the path or conductor to the ground and could get electrocuted.  It must be noted that all conductive material do not have the same conductivity and similarly not all insulators have the same level of insulation. Conductivity and insulation also depends on physical dimension of the material.  Two wire of same length but with different diameter, the wire with bigger diameter is a better conductor than the wire with lesser diameter. Similarly two wires of same diameter but with different lengths then the wire with shorter length has proved to be a better conductors than the longer wire.  SHORT QUIZ Get 1/4 sheet of paper 1/4 sir? Yes 1/4 1)____ allows most electricity to pass through them. a)Insulators b)Conductors c)Semi-conductors d)None of these 2. ________ move freely in conductors which allow flow of electricity. a. Atoms b. Protons c. Current d. electrons 3. _______ has zero resistance. a)Super-conductors b)Water c)Ice d)Silver 4. Super conductors work only at temperature below ______ o a)-200 F o b) 200 C o c) 200 F o d) -200 C 5. _______ does not allow electricity to pass through them. a)Water b) people c) animals d) Plastic 6. _______ does not allow electricity to pass through them. a)Water b) people c) animals d) Plastic 7. _______ is a perfect conductors. a)insulators b) semiconductors c) Superconductors d) none 8. TRUE or FALSE: Aluminum is cheaper than silver. 9. TRUE or FALSE: Aluminum is a better conductor of electricity compared to copper. 10. TRUE or FALSE: Pure water conducts electricity.