Planes, ships, our mobiles phones use electricity and I am sure they do not connect to ground. Why ?
2007-04-26 22:04:36 · 7 answers · asked by MU fan 1 in Science & Mathematics ➔ Engineering
because if a large electrical surge or spike enters the system, it must go to the ground. It can do this via a few ways. It will always take the path of least resistence. If you have a ground, it will use that pathway instead of your refridgerator, your vacuum, or possibly you. Cell phones do not need a ground. By definition the ship is grounded as it sits on the "Ground" of the water. Now planes do not need a ground either as the current will pass through the plane and dissapate. When on the ground, the plane is "Grounded" and when in the air, everything in the plane is grounded to the structure but the structure cannot be grounded when in flight. You are and electricakl student? You need to reread your books.
2007-04-26 22:18:47 · answer #1 · answered by daddyspanksalot 5 · 1⤊ 0⤋
Take the example of a PC, running (over here anyway) on 230V AC. Suppose the PC is getting old, some of the soldering is wearing out, and one of these joints is a live wire.
The AC circuit is made up of a live and a neutral feed - the neutral is fairly close to earth potential, and the live feed alternates above and below at an RMS 230V.
Without a safety connection, if the loose live wire was to touch the metal casing, and then I was to touch the metal casing, that circuit could be completed by going from live, through the case, through me, to earth.
Add the earth connection and the case is already at earth potential - so very little current through me, and most likely the mains circuit-breaker will have already tripped.
Cars, boats, planes, space-stations, etc use the chassis/hull/fuselage as 'earth' potential - so that all the metal bits you might touch are at the same voltage as your what your feet are standing on. However, this may not be the same as earth potential, so (as pointed out by another contributor above) it may be necessary to connect the two together prior to refuelling, otherwise sparks may be generated by the first object to connect the earth to the vehicle. You really don't want that object to be a fuel pump...
2007-04-27 13:46:50 · answer #2 · answered by nibblesthemouse 4 · 1⤊ 0⤋
Electrical systems are grounded to earth in an attempt to limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and to help stablize the voltage to earth during normal operation.
See Section 250.4(A) of the National Electrical Code for grounding performance criteria.
2007-04-27 01:11:10 · answer #3 · answered by Bryan H 3 · 0⤊ 0⤋
All the things you mention do have a point of common potential, usually the hull. Without a system of grounding or earthing we could potentially be surrounded by deadly voltages and be unaware until we made contact with them.
BTW, before an aircraft is refueled, a grounding strap is connected to the airframe.
2007-04-26 22:16:57 · answer #4 · answered by Helmut 7 · 0⤊ 0⤋
We need earthing for appliances like electric iron, stabilizers, fridges or any such appliances so that if the live wire comes in contact with the metallic body, the current is safely grounded to earth and you don't get any electric shock..
2016-03-18 22:04:49 · answer #5 · answered by Anonymous · 0⤊ 0⤋
to avoid the dangerous voltages and it prevent user contact with dangerous voltage if electrical insulation fails.
2014-12-25 23:01:35 · answer #6 · answered by kumkum 1 · 1⤊ 0⤋
we can save our electrical items from thundering lighting
2007-04-26 22:28:12 · answer #7 · answered by rajaratnam s 2 · 0⤊ 0⤋