Ask Me Anything...I Have An Answer

[Anynym]

Theoretical (not imaginary) is a term we (students/teachers) to describe circuit design involving mathematical results as opposed to measured results.

You may not miss anything - if a transformer has a no current in the secondary does the ratio of windings have any effect ? The coupling is a changing magnetic field driven by current but there is no current so I was leaning on zero. I guess I should have worded the question - If I have a neon pilot tube that will fire at 90 volts across the transformer - will it light up ? That was my thought behind the question.

Still more discussion relying on an ideal circuit when in reality even the best conductor has some resistance, and therefore some losses from heat energy.

The 60-watt light bulb may be engineered to present a particular resistance at a particular voltage, but as it also is engineered to give off heat and light the actual resistance will not be fixed but will instead be a function of the applied voltage. And as was already mentioned, the excess heat produced by applying an overvoltage will quickly burn out the conductor, resulting in Path Loss being presented as the surviving load.

That is, even if the (energized) wires coming out of the transformer are not connected to anything, they are still presented with a high-resistance load through the air, ground, and any other medium which forms a path for electrons. Just because air is a very poor conductor doesn't mean it does not conduct electricity.

My question, therefore, is: what is the air speed of an unladen swallow?

 

[jackson11]

Go for it....!

What does blue smell like?

 

[buttercup]

You may not miss anything - if a transformer has a no current in the secondary does the ratio of windings have any effect ? The coupling is a changing magnetic field driven by current but there is no current so I was leaning on zero. I guess I should have worded the question - If I have a neon pilot tube that will fire at 90 volts across the transformer - will it light up ? That was my thought behind the question.

Yes, if you connect the neon lamp across the 2ndary terminals, it will draw a (small) current, and it will light up.

The terminals of the 2ndary coil may be compared to water in a tap. Even if the tap is turned off, still the water behind the tap is under pressure. Same with the 2ndary coil. Even if no current is flowing, still the potential of 240 volts is there, ready.

Electric current (amps) is equivalent to the flow of water. Voltage is equivalent to water pressure. Electrical resistance (ohms) is equivalent to friction in the pipe.

If you put a load of any kind across the 2ndary terminals (being the kind of load that can respond to 240 volts), current will flow through the load -- the amps being determined by the amps = volts / ohms law.

Same with a voltmeter. If the terminals of the 2ndary coil are open, and you connect a voltmeter across them, the voltmeter will register 240 volts - but the voltmeter works by drawing a current, in order to do that.

Same with your fingers. If you span the 2ndary terminals between your finger and thumb, at 240 volts (don't try this at home), you will get a nasty shock. You get the shock because a current flows through your hand. (Note: If you walk across a nylon carpet, you can build up a static charge of several thousand volts, and when you touch the door handle, you can get a zap. But in that case, the current flowing through your body is minute, and the zap does you no harm. It's not the volts that kill you, it's the amps.

 

[IM469]

Yes, if you connect the neon lamp across the 2ndary terminals, it will draw a (small) current, and it will light up.

It will not draw current until the gas is ionized which occurs when the voltage is greater than 90 volts. The result is there is no load (no current) until the neon bulb fires. I hadn't given it much thought when I asked the question initially but I would have reasoned that the secondary voltage is zero independent of the windings because zero is a steady state like DC voltage and without an a changing magnetic field - I can't see how a voltage would exist on the secondary.

Your tap and water pressure analogy is valid in a closed circuit but we are dealing with two isolated circuits coupled by a magnetic field. I will bow to your position that there is 240 volts because I don't 100% know but your logic hasn't been any help convincing to reach the facts as you state them..

 

[IM469]

This neon lamp would draw current instantly

This would light only if 90 Volts was present. Think of lightening - the discharge isn't continuous but is built up until the threshold is reached - like a neon light. If you try to measure a neon light with an ohm meter - you will get no reading because the voltage used to measure resistance is too low to fire the neon light.

So if the 240 volts was on the secondary - it would fire - then - draw current. If without current (steady state) - the secondary had no voltage - the neon will not fire and cannot draw current.

I have a few of these as pictured from my old electronics days - I should try it out.