# what is the voltage across R252 & R253. Please do the needful asap. Thanks in advance!!

Discussion in 'Homework Help' started by veeresh540, Dec 17, 2014.

Dec 17, 2014
13
0
Hi,

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2. ### ericgibbs AAC Fanatic!

Jan 29, 2010
2,599
394
hi,
For two series resistors, Vjunc = Vin * Rtop/[Rtop +Rbot] ,assuming the junction is not loaded with another resistance.

Is this Homework.?

3. ### veeresh540 Thread Starter New Member

Dec 17, 2014
13
0
Hi,
Thanks for the quick response. Its required for my project. So,I need the voltage values across them in order to verify with mine. Please do the needful!!

4. ### ericgibbs AAC Fanatic!

Jan 29, 2010
2,599
394
hi,
Using the formula I posted, what do you calculate the voltage to be.? lets see your answer.
E

5. ### veeresh540 Thread Starter New Member

Dec 17, 2014
13
0
hi,
For R252, V=5/11v
For R253, V=50/11v

Am i right?

6. ### veeresh540 Thread Starter New Member

Dec 17, 2014
13
0
hi,
across 252 - 0.45V flows
across 253 - 4.55v flows
Am i right?

7. ### ericgibbs AAC Fanatic!

Jan 29, 2010
2,599
394
Hi.
Vout = Vin * 100k/[100k+10k] , so Vo = 5v * [100k/110k], = 5v * 0.909' = 4.54' Volts.

This of course assumes the ON pin has a very high input impedance [ resistance]

Does this help.?
E

8. ### veeresh540 Thread Starter New Member

Dec 17, 2014
13
0
hi,
Voltage at the R252 is 5V only right. The circuit acts as voltage divider and we will get voltage divider output at the R253 and after the resistor R252.
So for calculating the power dissipation of R252 we should consider the voltage passing through the R252.
We will get potential divider output after R252.

Is my analysis right?? Please clarify me!!

9. ### ericgibbs AAC Fanatic!

Jan 29, 2010
2,599
394
hi,
The current thru the 10K and 100K in series is 5v/110k is 45 micro amps!
So the voltage drop across the 10K is, 0.000045 *10,000 = 0.45'v and the 100k is 0.000045*100,000 = 4.54'v

Dissipation 10k = 0.000045 * 0.45 = 20 micro Watt and the 100k= 0.000045 * 4.54 = 204 micro Watts

BTW:
the voltage passing is incorrect, the voltage is across a resistor, the current 'passes' , flows thru a resistor.

10. ### vishal12345 New Member

Dec 16, 2014
8
1

first get the difference between these two protocol here
it will clear your basics i think

http://www.firmcodes.com/difference-rs-232-rs-422-rs-485/

11. ### djsfantasi AAC Fanatic!

Apr 11, 2010
2,911
881
He is not referring to communications protocols.
R252 and R253 are the labels for two different resistors on his schematic.
They are not the names of any protocols.
I doubt the link you provided would be useful.