What is the Electric Potential Difference Between "E" and "F"?

It appears that nodes A, B, C and E are just the same node. It also appears that O and F are the same node. So V_AO = V_BO = V_CO = V_EF

Connecting nodes A,B,C, is it short circuit?

as your inference,V_{EF=220v,but I do not think it is that simple...}

Redfred is correct.

If the squiggly things in AO, BO, and CO are producing electricity; then yes, there is a short circuit (actually 3). But not if the item in EF is producing the electricity.

What are you trying to do Fegor. This diagram is pretty senseless as AO, BO and CO are all in parallel ie A,B and C are shorted together so that F is O and E is A, B and C at the same time.

Is ABCO a transformer, motor, generator...? Is EF a lamp, valve, voltage source or just a circle with an X in it?

Seems to me that you are trying to represent a situation that you have with a diagram and haven't quite got it penned correctly.

We all want to help you here.

ABCO is a generator..

EF is a lamp

This is a schoolwork in high school book and the answer is Uef=0

I have some confuses about that so ask it here..

Here's a clue/question to help you understand (maybe) why the correct answer is 0V.

• If this is all connected as shown what current will flow through the lamp?
  

It is clear now..Thank you ^_^.

In that case, U_AB = U_BC = U_CA = 220√3 ≈ 380v. This is 3 short circuits. If things burn up, or the generator stalls, U becomes zero everywhere. This sounds like a trick question, not really fair in a high school book.

yes,I think the author of this topic is a little quirky(May be he/she wants to show other meanings ..)

it definitely appears in senior grade two book(physics)...

Not sure where Fegor is doing his High Schooling but yeh, this is not a basic electrical principals question.

In any event , U_AB = U_BC = U_CA= 220 CANNOT be true if AB, BC and CA or zero ohm.

The 220√3 value is only true if this is a polyphase AC circuit which you (we) are guessing it is by virtue of the appearance of the setup. If it was DC then there would be no fire if the polarities were the same way around and the lamp would then illuminate and the voltage would be 220Vdc.

The voltages post burn up would depend on where things opened first.

Tough one for high school.

Is that all the info that was presented in the question Fegor? What was the subject matter (text book chapter title) that this question was supposed to check your comprehension of?

I am in China.

Later I will upload a pic of this topic..but the context is Chinese...

Imagine each winding A, B & C to be a voltage source in series with a resistance.

Point E is then the neutral point of a star connected load.

Point O is the star point of the supply and is zero volts.

For a perfectly balanced load with zero resistance connecting wires, point F is the same as point O and is therefore zero volts.

The voltage difference between E and F is therefore zero.

However there will be current flowing through A, B & C and will depend on the voltage and the resistance.

This gives the power and therefore the heat generated.

If the heat is not adequately dissipated then the windings will combust.