05-01-2018, 04:28 PM
*Lightning conductor was invented by
Ans : Benjamin Franklin
*The liquid which conducts electricity but does not undergo electrolysis is
Ans : Mercury.
*Salt water conducts electricity depending on the concentration of dissolved salts.
*Substance which does not allow the flow of current through them is called - insulator eg: Glass, dry wood, dry paper, plastics, porcelain, mica, rubber, nylon, dry air etc.
*The commonly used insulator in electrical systems is porcelain or glass.
*The substance which partially conduct electricity is called - semiconductors.
eg: Germanium, Silicon
Resistance
*Resistance opposes the flow of electric current in a circuit.
*Resistivity is the opposite of conductivity.
*Conductivity is inversely proportional to the resistance.
ie; 1 siemens = 1/ ohm-1 = mho
*A filament of 60W bulb is thinner than the filament of 10GW bulb.
*If two bulbs of 60 W and 100W are connected in parallel, then the 100W bulb will glow more.
*If two bulbs of 60W and 100W are connected in series, then the 60W bulb will glow, more because the resistance of 60W bulb is more than that of 100W bulb.
Super conductivity
*At very low temperature most of the metals, allow current to pass freely through them. This phenomenon is called superconductivity and such materials are called super conductors.
*Super conductivity was discovered by the Dutch Physicist Heike Kamerlingh Onnes.
*Super conductors possess zero resistance at very low temperature.
*Ceramics is a superconductor above 100 K.
Electrical Power Transmission
*Most widely used current in domestic purposes is AC
*Electricity for domestic purpose is measured in Kilowatt hour (KWh) and are commonly called as ‘units’-lKWh = 1000 watt x 3600 seconds.
*KWh is also used as the commercial unit of electrical energy
*Electric power transmission was developed by Thomas Alva Edison.
INFO PLUS
*The supply voltage produced in India is 11 KV (Kilo Volt) or 11,000 volt.
*Voltage of electricity supplied for houeshold use in India 220-230 volt
*The frequency of household electric current in India is 50 Hertz
