Conductors and insulators

Conductors and insulators

1. Satale Coaching Classes Conductors And Insulators

2. Satale Coaching Classes Introduction

3. Conductors: Materials which allow electric current to flow through them easily are called conductors. Every material is made up of atoms which are tiny particles invisible to the human eye. Electron is one of the component of an atom. Electron of different types of atoms have different degrees of freedom to move around. In a conductor, the outer-most electrons of the atom are loosely bound and can freely move through the material when an electric charge applied. Thus electricity can pass through them.

4. 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.

5. It is an excellent conductor of electricity and is affordable. All the electric wires are generally made from copper. Even though carbon and graphite’s are non-metals, they are good conductors of electricity.

6. Insulators : Insulators are opposites of conductors. 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 cove materials that carry electricity.

7. Superconductors: Though metals are good conductors of electricity they are not perfect conductors. Some current is lost in the transfer as there is some resistance to the flow of current. A superconductor is a materials that is a perfect conductor. It has zero electrical resistance. Superconductors are usually a mix of two or more metals. However these are not superconductors at room temperature. They show zero resistance to electric flow at very low temperature usually below -200 o C.

8. Important facts: Like electricity heat can be conducted as well. Most electrical conductors are also excellent conductors of heat as well. Temperature plays a very important role in the conductivity capabilities of a material. In general the higher the temperature the lower the conductivity as resistance increase with temperature and vice-versa. Aluminium is a cheaper option to make wires compared to copper, however is not good conductor as copper. This will save costs for wiring however will increase consumption of electricity.

9. Conductors Fair conductors Good Insulators Common conductors and insulators: Silver Carbon Oil Copper Human body Fur Gold Moist human skin Silk Aluminium Acid solution Wool Magnesium Salt water Rubber Tungsten Earth Glass Nickel Water vapour (in air ) Plastic Mercury ----- Wood Platinum ----- Paper Iron ----- Wax

10. 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 then 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 then the longer wire.

11. The electrical properties of some material differ under different conditions. Most materials are poor conductors at high temperatures and god conductors when cooled. Some of the materials are pure conductors at extremely low temperatures which we call super conductors. As the electrons in conductors are free to move, such electrons can be forced to move in a direction. As electron move forward it pushes the electron in front of it, which in turn pushes the electron in front of it and all such electrons move forward in a group. This is what we call electric current or electricity. The path thus decided is what we call electric circuit.

12. Satale Coaching Classes Multiple Choice Questions

13. ____ allows most electricity to pass through them. Insulators Conductors Semi-conductors None of these 2) ________ move freely in conductors which allow flow of electricity. Atoms Protons Current Electrons b) Conductors d) Electrons

14. 3) _______ metal is a bad conductors of Heat Steel Aluminium Mercury Wood 4) _______ has zero resistance. Super-conductors Water Ice Silver 5) ______ allows some electricity to pass through them. Insulators Conductors Semi-conductors None of these c) Mercury Super-conductors c) Semi-conductors

15. 6) Super conductors work only at temperature below ______ -200 o F b) 200 o C c) 200 o F d) -200 o C 7) Electrons are stable in __________. Insulators b) conductors c) Semi – conductors d) none of these 8) _______ does not allow electricity to pass through them. Water b) silicon c) Graphite d) Plastic d) -200 o C a) Insulators d) Plastic

16. 9) ______ does not allow electricity to pass through them. Insulators b) conductors c) semi-conductors d) none 10) _______ is a non-metal though a good conductor of electricity. Steam b) wax c) Carbon d) rexene 11) When temperature increases, registance _______ Increases b) decreases c) Remains same d) none Insulators c) Carbon a) Increases

17. 12) ______ are used in mobile phones. Conductors b) insulators c) Semiconductors d) superconductors 13) _______ is a perfect conductors. insulators b) semiconductors c) Superconductors d) none 14) ________ behave in between the conductors and insulators. Aluminium b) copper c) Gallium d) semiconductors c) Semiconductors c) Superconductors d) semiconductors

18. 15) _______ are usually a mixture of two or more metals. superconductors b) conductors c) Insulators d) semiconductors 16) Aluminium is cheaper than silver. True b) false 17) Aluminium is a better conductor of electricity compared to copper. True b) false a) superconductors a) True b) false

19. 18) Silver is the best conductor of electricity compared to others. True b) false 19) Pure water conducts electricity. True b) false 20) Electrons are the only part of any atom. True b) false True b) false b) false