why dc ckts are not grounded thru ground?

Question

as in ac ckt the neutral is gnd why not in dc negetive gnd thru earth

Answer 1

AC does not necessarily have to use the earth as its reference - although in general it does. It is VERY undesirable to have a voltage (potential difference) between the AC reference and the actual earth because it increases the likelihood of electrocution. If it weren't referenced to ground, chances are somebody, somewhere accidentally referenced it to ground somehow. The ground will have a gradient across it and you could be zapped pretty bad a few miles from where somebody inadvertently referenced it to the earth. The safest way by far is to reference it to the earth at every residence to avoid large voltage gradients from building up.

DC circuits on the other hand need a path back to the other terminal of the battery (or source) in order for current to flow. There is no reason necessarily to reference DC to the earth but there is no problem in doing so. Sometimes it is preferable to completely isolate the DC circuit from the noise on the AC line - so it is not referenced to the earth. "Ground" is used as a general term to refer to the reference point for the voltages in the circuit - and may or may not refer to earth.

In all reality, the issue of earth grounding has nothing to do wth AC or DC, it has to due with power distribution. Most AC circuits are part of a power distribution network where earth grounding is used for safety whereas most DC circuits are localized so earth grounding doesn't yield any benefits.

Answer 2

First you must be clear why the ac ckts are grounded. The definition of AC itself clearly states that it will vary with time and the environment is also supposed to change with time. "The earth is an infinite capacitor". Plz remember this. that is why we rely on the ground to take up the extra voltage that may cause damage to the circuit and the user. But DC will not vary with time and hence does not cause any harm. Even any fluctuations that occur will be handled by the coupling capacitor we use to couple the source and the circuit. the capacitor will filter out ac components. Moreover the electrical devices have a maximum voltage rate of 230 to 260 v. but the dc rating of the devices will be much higher than the current that will be generated during any mishap.

Answer 3

One reason ac circuits are grounded is that they are exposed to lightning and grounding minimizes the possibility that electrical appliances in homes can attain dangerous potentials. DC circuits do not have the same exposure. Often DC circuits are referred to as being "grounded" but this usually just means that there is a common path in the circuit which usually includes the circuit chassis. Earth grounds are sometimes used but not necessarily for safety.
Please see:
http://cipco.apogee.net/foe/fctgc.asp

Answer 4

Mostly because the return path for a DC circuit is back to the battery or a power supply.