[Systems Engineering Teachers' Mailing List] RE: syseng Digest, Vol 28, Issue 12 Practice exam errors

[Powell, Warren S]

Paul,
I also have notified them of the wrong answers and have had no reply.
In regard to Q12 the speed will not change. Only the diameter of the drum will change due to the cable coming and going. The drum is spinning on an axis therefore the speed will not change. The torque might increase a little.
Hope this helps.

________________________________

From: syseng-bounces at edulists.com.au on behalf of Barton, Paul S
Sent: Tue 10/30/2007 8:46 AM
To: syseng at edulists.com.au
Subject: RE: syseng Digest, Vol 28, Issue 12 Practice exam errors


I have asked Lorraine Tran and Kristen Allen for an answer sheet to the practice exam questions over 4 months ago, as I also found problems with the practice exam. I agree with your findings on questions 6,7,11, question 9 I'll defer to your Knowledge. I also asked about question 5 (subjective), Question 3 (formula should be Force= pressure X area), section B q1,I found I needed 3 pads and q12 the speed would be the minimum as the drum diameter increases so would the speed. I have also stated the correct vr ratio should be driven over driver if we are to comply with industry standards.
 
Paul Barton
Technology teacher
Dromana Secondary College

________________________________

From: syseng-bounces at edulists.com.au on behalf of syseng-request at edulists.com.au
Sent: Mon 10/29/2007 12:00 PM
To: syseng at edulists.com.au
Subject: syseng Digest, Vol 28, Issue 12



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Today's Topics:

   1. Practice Exam errors (Robert Minato)


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Message: 1
Date: Mon, 29 Oct 2007 09:43:06 +1000
From: Robert Minato <rminato at ccw.vic.edu.au>
Subject: [Systems Engineering Teachers' Mailing List] Practice Exam
        errors
To: "syseng at edulists.com.au" <syseng at edulists.com.au>
Message-ID: <7878124.6681193611395403.JavaMail.root at localhost>
Content-Type: text/plain; charset=US-ASCII

Had a look at the new practice exam on the vcaa website. There are a few
problems with it:

Section A
Q6. Symbol for a voltage reg is not on the vcaa symbols list. Responses A, B
and D all represent another component, so by default, Response C is left
which must be the correct answer.
Q7. 120 and 600 Ohm in parallel gives 100 Ohms. 12V/100Ohms = 120 mA. No
correct response.
Q11. Brown Green Yellow resistor is 150 kOhms. No correct response.

Section B
Q9. The motor will only ever rotate in one direction. The back emf diode
will be forward biased in one switch position effectively shorting across
the motor. [Depending on the current supply and diode rating, the diode may
burn-out, in which case the motor will then work in the second direction.
Back emf diodes normally used when other components (eg transistor) are in
circuit to prevent damage.]

Formula sheet
The resistor colour code needs a multiplier column. Unless a great deal of
time has been spent with the code, most students would nave some trouble
with the multiplier. Probably explains the confusion with Section A Q11.

Rob


--
Robert Minato
Technology Leader
Catholic College Wodonga
1 Bowman Crt
Wodonga 3690
02 6043 5546




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