# Help with these circuit equations!

Discussion in 'General Electronics Chat' started by Jsean21, Jan 9, 2009.

1. ### Jsean21 Thread Starter Member

Jan 8, 2009
20
0
If R is 30k(ohms) and R2 is 10k(ohms), calculate the resisitance of R3 is V3 is to be 2V and the Vt(t=total, supply voltage) is 10V?

What other resistor values could be used for R1, R2, and R3 but still ensure V3 is 2V if Vt is 10V

i do electronics at college we've been given this worksheet on resistors and im absolutley baffeled on what i have to do, please can somebody give me the solution to this equation and explain how?

2. ### mik3 Senior Member

Feb 4, 2008
4,846
69
I think you are talking about a voltage divider circuit. The voltage across R3 will be

VR3=(V*R3)/(R1+R2+R3)

where V is the supply voltage

The rest is calculations, try it.

3. ### Jsean21 Thread Starter Member

Jan 8, 2009
20
0
erm i understand what u mean but how exactly do we find R3 using the information from the question? also the circuit involved testing the voltage of resistors in a series circuit

4. ### mik3 Senior Member

Feb 4, 2008
4,846
69
Solve the equation for R3 and plug the values of R1, R2, VR3 and Vsupply into the equation.