# Help with Physic project

Discussion in 'Physics' started by redwood4545, Apr 11, 2013.

1. ### redwood4545 Thread Starter New Member

Apr 11, 2013
2
0
Hello all,

I am having trouble with a science project. I am suppose to figure out how many volt an electric fly swatter produces. I am planning to figure out the voltage using the transformer and the induction law. But i am having trouble trying to figure out the loops in the transformer. The fly swatter was purchase from freight harbor tools. the Transformer has a yellow band on it. http://forum.allaboutcircuits.com/attachment.php?attachmentid=2423&d=1205283422 as seen in this picture.

Please friend help!!! i need to turn the project in friday this week =(

2. ### russ_hensel Distinguished Member

Jan 11, 2009
820
47
Would you consider measuring it, I think a transformer calc would be inaccurate because the wave forms are not sinusoidal.

3. ### redwood4545 Thread Starter New Member

Apr 11, 2013
2
0
How would i measure it?

4. ### davebee Well-Known Member

Oct 22, 2008
539
46
That circuit looks like a one-transistor oscillator with a transformer that feeds the high voltage AC to a rectifier circuit to that large capacitor, so there may be a DC voltage available for measuring.

There are DC voltmeters that measure into the thousands of volts; that would be the best way.

Or you could estimate the voltage based on the length of spark. I think that estimate can get pretty close if the spark is between spheres of a large radius; the estimate of voltage for spark length of between sharp pointed wires won't be as good.

3000 volts per millimeter of spark is a number I've seen.

5. ### russ_hensel Distinguished Member

Jan 11, 2009
820
47
If it is dc you can measure it with a normal voltmeter and a voltage divider. By measuring with two different impedances on the volt meter you can get the source impeadance and calculate the no load voltage. I have left a lot of the details to you.

6. ### WBahn Moderator

Mar 31, 2012
18,079
4,917
I cuncur with Russ. You might use several resistors in series to minimize the voltage dropped over each one so as to prevent arcing over the resistor.

7. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
515
I note this request was posted on Thursday 11 April with the intention of project fulfillment by Friday, the following Friday being the 12th!

Redwood, whilst you are very welcome at AAC, it is inadvisable to leave things so near the deadline.

The question itself is quite interesting and it has been suggested to measure with some sort of DC voltmeter.

The swatter produces pulses at high voltage, which are frequently discharged.
I suspect the pulses would be too fast for a DC measuring system. Otherwise a simple electrostatic meter might suffice.

I further think that the college would have health and safety issues with direct connection via heath robinson lash ups - these swatters can pack quite a bite.

However if the college also teaches auto engineering help is at hand since a standard engine oscilloscope would be just the ticket to capture and measure the pulse and provide the necessary well insulated high resistance attachment leads.

go well