Household Circuits

bingus

Power distribution

________ to a house:: Pole /source- high rated fuse (company fuse) connected in the live wire- kWh meter- main switch connected in both live and neutral- main fuse (MCB) connected in live wire- different parts of the house.

hollow insulating

A hole nearly 2- 3m deep is dug and a copper rod covered by a(n) ________ pipe is inserted.

fuse

The use of a(n) ________ safeguards the circuit and the appliances connected in that circuit from being damaged.

current stops

The ________ flowing when the fuse breaks, but the appliance remains connected to the high potential point of supply through live wire.

MCB

________:: modern alternative to the traditional fuse, it trips to switch off the circuit in a very short time (25ms) It is more convenient than fuse wire because it does not need to be replaced, and it is safer due to the quick response.

Ac voltage

________ is used because:: it is not possible to step up or step down a d.c. current.

thick copper plate

A(n) ________ is welded to the end of the rod and buried surrounded by a mixture of charcoal and salt and water is poured to keep the ground damp.

High tension wires

________:: for high voltage and heavy current, ________ are used which have low resistance and large surface area to reduce heating.

pin

Three ________ plug:: plug where the top pin is for earthing, left is for live and right is for neutral.

fuse

Electric ________:: a safety device which is used to limit the current in an electric circuit.

Power Station

11kV

Benefit of high voltage

P = VI, for a given power P, I = P/V

a.c. voltage is used because

it is not possible to step up or step down a d.c. current

Grid Substation

Step up from 11kV to 132kV

Main Substation

Step down from 132kV to 33kV

From Main Substation

33kV current supplied to heavy industry and intermediate substation

Intermediate Substation

Step down from 33kV to 11kV

From Intermediate Substation

11kV current supplied to light industry and city substation

City Substation

Step down from 11kV to 220V, supply to domestic consumers

Ring system

System where a separate ring is used for each portion of the house

Advantages of ring system

1) Current from mains can take two paths to reach each appliance, therefore lower current carrying capacity wire can be used, reducing the cost

Advantages of connecting appliances in parallel

1) Each appliance gets connected to 220V supply

Disadvantages of connecting appliances in series

1) The voltage of the source gets divided in all the appliances in the ratio of their resistances

Electric fuse

a safety device which is used to limit the current in an electric circuit

Rise in temperature of a fuse depends on

current rating I and radius r. Does not depend on length of wire

Current rating of fuse

Total power of appliances in circuit / voltage of supply

MCB

modern alternative to the traditional fuse, it trips to switch off the circuit in a very short time (25ms) It is more convenient than fuse wire because it does not need to be replaced, and it is safer due to the quick response

Switches

on-off device for current in a circuit, connected in live wire

Reasons for switch to be connected in live wire

If the switch was connected in the neutral wire, the appliance would remain connected to the high potential point of the live wire even when the switch was off, and if a person touched the appliance they could get an electric shock

Local earthing

done near the kWh meter

Earthing of an appliance

Earth wire of the cable is connected to the metallic case of the appliance

Three pin plug

plug where the top pin is for earthing, left is for live and right is for neutral

High tension wires

for high voltage and heavy current, high tension wires are used which have low resistance and large surface area to reduce heating