Pre-exam questions!

[Guest Luke]

Hey guys,

 

I have a Core Engineering exam tomorrow, and theres a few questions from past papers that I'm stumped on. If someone could give me some tips today that would be great.

 

• How are rails in railway tracks made?
  
• How do the relative costs of initial setup, tooling and materials change with the number of components and manufactures?
  
• How does the molecular weight of a polymer affect its properties?
  
• How can I draw an FCC crystal and indicate it's Miller incide on the same diagram?
  
• Name and sketch the process by which most domestic ceramic products are manufactured
  
• Give an example of a simple forged component and sketch the important features of the dies you think could be used to forge it.
  

 

Also, if anyone can give me a quick summary on transistors?

 

I know that Base Current = Voltage - 0.65 / Base Resistor

 

Is the Collector Current simply Base Current * Beta?

 

Where does the Collector Resistor come into things? And how is the Collector Voltage worked out?

 

If anyone can answer just one of these questions it would be a great help.

 

Thanks guys!

[Douglas]

Also' date=' if anyone can give me a quick summary on transistors

I know that Base Current = Voltage - 0.65 / Base Resistor[/quote']

If this means that there's .65V dropped across the base emitter junction, then yes.

 

Is the Collector Current simply Base Current * Beta?

Yes, very close. the collecter and emitter current are almost the same.

 

Where does the Collector Resistor come into things? And how is the Collector Voltage worked out?

The collector resistor is selected to bias the transistor in it's operating point. The collector voltage is simply the collector current times the collector resistor. V=IR. That is to say, the base voltage is known, (you selected it), then with .65V dropped across the base/emitter junction, the emitter voltage is known, thus the emitter current is known, thus the collector current is known, and the collector resistor is known, and the supply voltage is known, so the collector voltage is known.

[Guest Luke]

Thanks for the tips.

 

THe Electronics and Materials sections went okay, but the Mechanics was really hard. It turns out the Mechanics questions were identical to last year - but I didn't try last year's paper. Looks like I'll be the only one not getting full marks. Oh well, **** it.