Comp Sci Need help finding the resistor size for a circuit (Ohm's law)

[karumees123]

Homework Statement

Need help finding the resistor size for circuit

Relevant Equations

Kirchhoff's Current Law
Ohms Law

I know there is a serial and parallel circuit

I know R1 = 2k, R3 = 1k and i know Vout which is 1V. And i know 5V is coming from supply. I need to calculate the size of resistor R2.

I can calculate :
1) IR1 = 5-1V/2000ohms = 2mA
2) UR1 = 0,002A*2000ohms=4V voltage drop on R1

How do i go on finding R2?

Can somebody explain me with exact equations to calculate R2, and currents which run trough resistors (step by step please)

Help will be much appreciated!

 

[berkeman]

Homework Statement:: Need help finding the resistor size for circuit
Relevant Equations:: Kirchhoff's Current Law
Ohms Law

View attachment 270841

I know there is a serial and parallel circuit

I know R1 = 2k, R3 = 1k and i know Vout which is 1V

Can somebody explain me with exact equations to calculate R2, and currents which run trough resistors (step by step please)

Help will be much appreciated!

Welcome to PhysicsForums.

I'll try explaining it in words first, since you need to do the bulk of the work on your schoolwork problems here.

You are correct that R2 and R3 are in parallel. And you have an overall "voltage divider" from the input voltage to the output voltage based on the upper resistor and the parallel combination of the lower resistors.

Can you write the equation for a resistor divider based on the values of an upper and lower resistor and the input voltage? So what does that mean in this case where you have 5V in and want 1V out? What is the divide ratio? And what does that mean about the relative values of the upper resistor and the lower resistor(s) in the voltage divider?

Also, can you write the equation to use when forming the parallel combination of two resistors?