is this analogy is correct?

Discussion in 'Electronic Design' started by M.Parker, Jul 7, 2009.

1. M.ParkerGuest

This post has nothing to do the with different types
of batteries, just for circuit analysis I provided the below link
http://en.wikipedia.org/wiki/Daniell_cell

=> The positive connection of that yellow bulb
instead of connecting it to the copper electrode
if I connect it to the earth, the circuit is closed.

now, would the bulb illuminates or not?

no.

w.

3. M.ParkerGuest

why ?

if you connected it to earth, you need some way of getting the
is it really necessary.?

why do we need 2 wires to conduct electricity

http://en.wikipedia.org/wiki/Electric_locomotive
http://en.wikipedia.org/wiki/Pantograph_(rail)
I'm afraid that electric locomotives has single wire;
i.e. singlephase

6. M.ParkerGuest

Thanks Tom; you are quick and informative.

Small thought Experiment:

A rotating Magnetic field will create a Current in a wire(I said a
single long wire, not 2 pieces, no confusion here)

now, using this current in that single wire,
how to make the bulb illuminates?

If I connect the one end of the wire to the '+' of the bulb
and the '-' of the bulb to the earth.

By default, we are left with the other end of the wire as open.

There is Current in the wire by the effect of the rotating magnetic
field, it would pass through the '+' of the bulb and there by to
Tungsten(or whatever it is) and to '-' side of bulb there by to the
earth.

then, why can't the Bulb illuminates?
==========

Procedure (2)

Instead of 1 single long wire, If I take 2 pieces of wires

One to the '+' of the bulb,
other to the '-' of the bulb

at their both ends, if I joined them now the loop is closed.

If any rotating magnetic field produces the current in the wire
the bulb will illuminates.

but, not in the first case, why?

7. M.ParkerGuest

My one straight question..,

(q) why the path should be closed to illuminate the bulb?

8. Martin BrownGuest

One of the more spectacular examples is with fluorescent tubes under
pylons. Richard Box specialised in impressive dusk displays of this as
artist in residence at Bristol University Physics dept.

http://www.interactivearchitecture.org/richard-box.html

Regards,
Martin Brown

9. John KD5YIGuest

No, the rotating magnetic field will create an electromotive force or
potential (measured in volts) on the wire. The amount of current (measured
in amps) that flows in the wire will be a function of the load placed from
end-to-end on the wire (completing the circuit).

(remainder snipped due to invalid thought experiment assumption)

Thanks. Same to you.

John

10. M.ParkerGuest

Given my 2 hands,

one hand holding the electric wire on the pole and
the other touching the pole.

=> will I feel the electric shock or not ?

I touch only one wire, but not '2' as you people said for the
illuminating of the bulb :-(

11. M.ParkerGuest

Case(a):

If we connect the '+' end of the bulb to the one of the wires of the
electric pole and '-' to the earth, would the bulb illuminates or not?

Case(b):

If we touch the one of the wires of the electric pole with right hand
and the left hand to the Earth, would we feel the electric shock or not?

Both cases are same, but instead of the bulb, if we replace the it with
a human he can feel the shock, but the bulb will not illuminates.

what type of logic is this =-O ?

12. M.ParkerGuest

I will go with the II one; but, I want to hear more reasons
as I'm not completely satisfied :-\ with the above one.

so, at the end the conclusion is

Current is and will always present in "Closed" circuits. But, not in
open.

13. gregGuest

No, there isn't, at least not a continuous one.

A current will flow for a short time when the wire first
starts to move through the field. But electrons will start
to build up at one end of the circuit, and the resulting
negative charge will tend to stop further electrons from
flowing in. Similarly, the other end of the circuit will
acquire a positive charge due to electrons flowing away
from it, which will tend to attract the electrons back.
Soon an equilibrium is reached, and no more current flows.

If you close the circuit, then electrons can flow all
the way around without building up in any one place, so
a continuous current is possible.

14. gregGuest

Some current will probably flow, because the earth then
forms part of a closed circuit. Whether it's enough to
light the bulb depends on the conductivity of the soil
and the rating of the bulb.

15. gregGuest

That depends on how conductive the pole is. You
certainly have the potential to feel a shock, because
one side of the mains supply (called the "neutral")
is connected to the earth, and so is the pole.

I strongly recommend that you do NOT try this
experiment!

16. gregGuest

Potentially, yes. If the wire that you touch it to is
the "live" side of the supply, current will flow,
because of the neutral side being connected to earth.
If a current flows in one case, it will also flow in the
other case, although the amount of current will be
different, because most light bulbs have a much lower
resistance than a human body does from one hand to the
other.

Whether the current is enough to light the lamp or cause
the human to feel a shock depends on details such as the
conductivity of the pole and the soil.

17. gregGuest

Not always -- it's possible to have a closed circuit
with no current flowing in it.

What you can say is that it's *possible* for a continuous
DC current to flow in a closed circuit, but not in an
open circuit.