<P> A perfect insulator does not exist , because even insulators contain small numbers of mobile charges ( charge carriers ) which can carry current . In addition , all insulators become electrically conductive when a sufficiently large voltage is applied that the electric field tears electrons away from the atoms . This is known as the breakdown voltage of an insulator . Some materials such as glass , paper and Teflon , which have high resistivity , are very good electrical insulators . A much larger class of materials , even though they may have lower bulk resistivity , are still good enough to prevent significant current from flowing at normally used voltages , and thus are employed as insulation for electrical wiring and cables . Examples include rubber - like polymers and most plastics which can be thermoset or thermoplastic in nature . </P>
<P> A perfect insulator does not exist , because even insulators contain small numbers of mobile charges ( charge carriers ) which can carry current . In addition , all insulators become electrically conductive when a sufficiently large voltage is applied that the electric field tears electrons away from the atoms . This is known as the breakdown voltage of an insulator . Some materials such as glass , paper and Teflon , which have high resistivity , are very good electrical insulators . A much larger class of materials , even though they may have lower bulk resistivity , are still good enough to prevent significant current from flowing at normally used voltages , and thus are employed as insulation for electrical wiring and cables . Examples include rubber - like polymers and most plastics which can be thermoset or thermoplastic in nature . </P>
electric wires are covered with rubber like material give reason
electric wires are covered with rubber like material give reason
insulation
insulation