parallel resistor

[metelskiy]

Hello, I'm new to this community and to electronics. I need help with lab report that i need to do. here is the situation. I had to design a simple circuit voltage devider with 10V power source using only 2 resistors and output voltage to be 6V. So i figured out two resistors would be R1=3.9k and R=5.6k

Than in next lab we had to modify this circuit to make output voltage 5V instead of 6V by simply adding parallel resistor R3 across R2. By calculation i figured out R3 to be 11k.
Now in my lab report i need to explain everything. But i don't understand how adding 11k in parallel with R2 dropped voltage from 6V to 5V? Can someone please explain in details how did this process go? I thought at point A voltage should be 10V minus voltage drop across R1. Or if we have main source 10V and we need 5V between to resistances i thought those 2 resistances should be equal. please help.

 

[(*steve*)]

Look in the tutorials section here for a tutorial on resistors in series and parallel.

This one might help you. If there's nothing suitable in the tutorials section, google for "resistors in series and parallel"

 

[davenn]

Now in my lab report i need to explain everything. But i don't understand how adding 11k in parallel with R2 dropped voltage from 6V to 5V? Can someone please explain in details how did this process go? I thought at point A voltage should be 10V minus voltage drop across R1. please help

ok so did you so your resistors in parallel calculation to work out what the combined value would be ?

keep in mind that 11k Ohm resistors are hard to come by (maybe a metalfilm)
the standard value would be 12k Ohms use that

Or if we have main source 10V and we need 5V between to resistances i thought those 2 resistances should be equal.

That is true, do your calc and you mite be plesantly suprised with the answer

Dave