What do we mean when we say 'electical ground or earth in physics?

Answer 1

Ground is considered to be 0 volts.
In an external sytem, it may actually be connected to the ground, in a closed system, it is simply a reference point. Usually the negative pole is considered to be earth...

even on a battery (in a closed sytem, which has no connection to any other reference point) the negative is usually considered as 0 volts and positive is considered as the actualy voltage (say, 9 volts for a PP3 battery)
it would be just as correct to use the positive pole as + 4.5 volts and the negative pole at -4.5 volts
or to use the positive pole as 0 v and the negative pole as -9v

however, it would make things confusing if we all used different references, so, generally, negative = 0 V,

Answer 2

'Ground' is the reference point from where you can measure the voltages within your circuit. In a modern d.c. powered circuit it is normally taken as the -ve side of the power supply, then all voltages you measure are relative to this, and normally are +ve voltages. However, some circuits use the +ve side of the power supply as 'Ground', and so all voltages measured are then -ve.

In a circuit that uses a split power supply, 'Ground' is usually at the junction of the two supplies and then there are both +ve and -ve voltages around the circuit.

'Ground' or 'Earth' originally came about because either the equipment case or one side of its power supply was literally connected to the ground, or surface of the Earth using a long metal pole called an Earth Rod. This still happens today with the electrical circuits in your home. The idea is that both you and the circuit are in contact with the ground and thus at the same voltage potential. This way there is less chance of there being a large voltage difference between you and the circuit should the circuit develop a fault. If there is no voltage difference then no current can flow and you cannot get an electric shock. If there was a large difference then a current could flow through you if you touched the faulty circuit and BAMM! Nasty electric shock!

Answer 3

If you put the standard human digit onto mains voltage, current will flow through you to the earth. This won't do you a lot of good, more than about 50mA could kill you. (i.e. Only one twentieth of an Amp)

We connect any metal close to high voltages to earth to protect you. In a fault condition the current would most likely drain to earth via the earth wire. This earth wire should be capable of taking enough current to blow the fuse.

This is why Earth or Ground is such an important concept.

Answer 4

It means a "physical copper rod" driven into the ground of the earth and providing a set specific minimum resistance. Ground Rods driven into the earth must measure out a max. set resistance in order to be considered a ground rod. That ground rod then is referenced to a meter as ZERO reference point of voltage and infinite resistance between an object not ground and a grounded rod.

Electric company supplying you light and power has millions of ground rods to assure this is happening in their system.

Answer 5

The earth is our zero reference in electricity. All potential measurements are measured compared to the earth.

The earth or ground is used if we have too much electricity in our circuits. It's like an overspill.

Answer 6

It means that the user of the electrical equipment is well protected since the electrical current will flow to the ground directly without passing through his body and thus avoiding the electrical shock which may kill the user.

Answer 7

in the UK we use a 230 volt electrical supply that has the neutral connected to "earth" or "ground", this is to ensure that if any electrical device develops a fault it causes a immediate short circuit to trip the fuses, rather than the short circuit only being discovered when someone gets an electric shock.

Answer 8

Theres a metal plate in the ground and all the EARTH wires are conected to it to obsurb electricity.

Answer 9

I think that the electric supply has one end connected to the ground

Answer 10

Ground is a common connection and reference point from which voltages and signals in a 'system' can be measured from, and be relative to. 'Inputs' and 'outputs' to the system having a common connection to this point become referred to this point, rather than 'float' at an unknown voltage.