05-01-2018, 04:30 PM
* Instrument that measures the amount of electric energy used by a consumer - Watt hour meter (Electricity meter)
* In houses, electric wirings are connected in parallel because all the instruments in the house could get equal supply of electricity and stronger current for longer time.
Fuse
*A protecting device, which cuts off an electric circuit when high current flows through the wire
Ans : Fuse
*In an electric circuit, a fuse is connected in the live wire to avoid overloading.
*Copper or the alloy of Tin and Lead are the metals used in an ordinary fuse wire.
*A fuse wire is characterized by
Ans : High resistance & low melting point.
*Short circuiting is a high current produced in a low resistance circuit when two wires of main comes in contact with each other.
*When a charged body is connected to the earth it gets neutralised. This is called earthing.
*Electric fittings are earthed to prevent electric shock.
*MCB - Miniature Circuit Breaker (a small trip switch that stops the flow of electric current in an overloaded electric circuit).
*ELCB - Earth Leakage Circuit Breaker (safety device used in electrical installation with high Earth impedence to prevent shock).
*The earthwire and the fuse together protect the user and the electrical appliances
*Quartz crystal in watches work on the principle of peizo electricity.
*A cell uses chemical reaction to make electricity.
*A number of cells connected together are called battery.
*The negative electrode in a dry cell is cathode, eg: Zinc
* The positive electrode in a dry cell is anode, eg: carbon rod.
*The electrical device which is used to increase or decrease the amount of AC voltage between two circuits is - Transformer.
No Confusion
*Colour of positive wire in domestic circuits
Ans : Red/brown
*Colour of neutral wire in domestic circuits
Ans : Black / blue
*Colour of earth wire in domestic circuits
Ans : Green
EMF
*EMF (Electro Motive Force) or potential difference measured in volt is called voltage.
*The emf of a dry cell (torch cells, remote controls etc.) is 1.5 volts.
*The emf of a voltaic cell is 1 volt.
*Voltage of a. torch cell -1.5 volt.
*Battery used in mobile phones - Lithium - ion battery (3.6 volt)
