This circuit is used to demagnetize a television picture
tube each time the set is turned on. The coil surrounds the tube and is energized with an alternating current
that quickly decays to zero over a period of several seconds. Which of the following components would
you expect to find connected in series with this coil?
A. A step-up transformer C. A piezoelectric device
B. A Hall-effect device D. A PTC thermistor

I think its C, am I correct? Thanks for the help.

 

Hello,

You are not correct, a hall device is to measure the magnetic field.

What would be needed to cause a decreasing current in the degausing coil?

Bertus

 

Hello Bertus, this is why I posted this question. That is what I thought it was but on my test I was wrong. I answered "hall effect device" and it was graded as wrong. Why would that be?

 

Hello,

Take a look at this wiki page:
http://en.wikipedia.org/wiki/Degaussing

Bertus

 

Hello Bertus, this is why I posted this question. That is what I thought it was but on my test I was wrong. I answered "hall effect device" and it was graded as wrong. Why would that be?

Which of those answers would make the current decay over time? You already know it's not a hall-effect device. You have left the transformer, the piezo, and the thermistor. Which of the remaining three makes the most sense to you and why?

 

Rather an archaic question.

 

Guys I'm confused here and I agree its an archaic question. I thought it was Hall effects device, we are saying 100% its not right?
Step up transformer doesn't make any sense to me even though it deals with coils.
Piezoelectric makes no sense to me either.
Is it the PTC thermistor? Narrowing it down that is what i am coming up with.

 

Thank you Bertus, I appreciate that link. It is PTC thermistor. Sometimes I get set on an answer like with "hall effects" and overlook the others. Thanks again for the help.

 

Hello,

You are right now.
The PTC will increase its resistance (and lower the current) when the part gets warm.
There will be some equilibrium between the current and the temperature of the PTC.

Bertus

 

Excellent and thanks Bertus, appreciate the help. Stay tuned I may need more help in a few weeks or so.