resistors

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NWDS

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any one got the answer and how to get there ????????????.

calculate the value of a resistor wich, when connected in parallel with the given resistor, will produce the value asked for.

pls give answers to 3 sig figs

a, given resistance 48ohms resistance required 12ohms

regards Iain

 

Theorysparky

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1/12 = 1/48 + 1/?

1/12 - 1/48 = 1/?

0.083 - 0.0208 = 0.062

1/0.0622 =16 ohms

transposition of the equation got me to it

 

NWDS

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Thanks TS, I think I have it but Iam sure to be back when its volt drop.

regards Iain

 

NWDS

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Once again chaps a BIG THANK YOU !!!!!!!!!!!!!!!!.

regards Iain

 

NWDS

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sorry fellas but this one has me, I have done all the others ( with a lot of help from you guys ) and feel comfortable with that.

given res 0.6 cubed , res required 200,

0.6multi 0.6 multi 0.6 = 0.216, 1/0.216 = 4.269

1/200= 0.005

I have looked the answer up and I cannt get there any ideas ???.

Thanks again Iain

 
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In the office again.
IF we`re still on parallel - 1/r1+1/r2etc=1/rt

so 1/0.6 + 1/0.6 + 1/0.6 = 1/rt

ergo 1.67 (1/0.6) + 1.67 + 1.67 = 5.01

However - all that being said - resistances in parallel can NEVER be higher than the lowest resistance.

SO - if 0.6 ohms is the lowest, you`re never going to get 200 ohms out of it!!!

HOWEVER - if they are 0.6K ohms (600 ohms??)

3 equal resistances in parallel

= r/n

=600/3

=200

or: 1/600 + 1/600 + 1/600

=0.00499999 recurring

1/0.004999999999 = 200

QED

 

NWDS

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So sorry KME, I had lost the will to live and had not read the question correctly it sholud have been

0.6multi 10 cubed

0.6 multi 1000 = 600

1/600= 0.00166,

1/200= 0.005

0.005-0.00166 = 0.00334,

1/0.00334= 299.401 rounded up to 300 ( answer in the book )

regards Iain

 

Admin1

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Can I ask what book this is Please Iain?

 

NWDS

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Sure can Admin, elec calcs vol 1 7th edit page 35 ques 2 (g), Iam sorry for being dumb as s..t but we all have to start at the begining.

 
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Sure can Admin, elec calcs vol 1 7th edit page 35 ques 2 (g), Iam sorry for being dumb as s..t but we all have to start at the begining.
Phtt! :eek: :(

if you WERE "dumb as s..t"..

You would not be bright enough to ask for help!! ;)

As has been said before..

The Fik ones are thems wot don't ask!!!! :) :) :)

 

NWDS

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Thanks for the reassurance fellas, just what I needed.

regards Iain

 
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