CURRENT ELECTRICITY
Mind map of current electricity
● ELECTRIC POWER is generated at the GENERATING STATION at 11 kV and stepped up from 11 kV to 132 kV
● EARTHING: is done in a house near the kWh meter. Earthing is done for safety which puts the appliance at zero potential
●Colour coding: Live wire — Red or Brown
Neutral—Black or light blue
Earth wire — Green or yellow
●FUSE: “Is a device used to limit the current in an electric circuit”. The use of fuse protects the appliance in circuit from being damaged. Fuse is always connected in live wire. A fuse wire is an alloy of lead and tin has
(i) High resistance
(ii) Low melting point.
● Pole fuse has current rating 50A.
Two types of fuses used at home . One of Rating 5A and another 15A. Higher is the rating , thicker IS This the wire
●These days miniature circuit breakers (MCB) are used. It is AUTOMATIC CIRCUIT breaker, when current flowing in excess.
● Appliances in a house are connected in parallel.
1. 1 coulomb of charge = charges on 6.25 x 10¹⁸ electrons
2.Current Electricity is the rate of flow of charges. I= Q/t
4.Potential difference:- It is the amount of work done in moving a unit positive charge from one point to other.”
Potential difference V = Work done / charge moved
W = QV but I= Q/t
Hence, W = VIt
or Electrical energy = VIt
6.Power:- It is “Rate of doing work”
P = W/t = VIt/t
P= VI
7. Power is said to be one watt when one joule of work is done per second
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Points to be remembered
- S.I. unit of charge is coulomb (C).
- S.I. unit of current is ampere (A).
- S.I. unit of P.D. is volt (V)
- S.I. unit of electrical energy is joule (J)
- S.I unit of power is watt (W)
- 1 watt= 1 J/s
- Commercial unit of electrical energy is kWh.
1kWh = 3.6 x 10⁶ J
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To know
ELECTRIC POWER is generated at the GENERATING STATION at 11 kV as these stations are at very far off place from areas where it is to be used. The voltage (A.C.) is of 50 HZ frequency.
• This alternating current (A.C) voltage is stepped up from 11 kV to 132 kV to minimize the loss of energy in transmission line wires.
• At GRID-SUB-STATION this voltage is stepped down from 132 kV to 33 kV and transmitted to heavy industries and main SUB STATION
• At MAIN SUB STATION, it is further stepped down from 33 kV to 11 kV for supply to lighter industries and city sub station .
• At CITY SUB STATION, it is further stepped down from 11 kV to 220 V for supply to houses for consumers.
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Very informative
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