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

In summary, the problem involves finding the size of resistor R2 in a serial and parallel circuit, with known values of R1 and R3 (2k and 1k respectively) and Vout (1V). Using Kirchhoff's Current Law and Ohm's Law, the equation for a voltage divider and the equation for a parallel combination of resistors can be used to find the value of R2. The divide ratio between the input and output voltages and the relative values of the upper and lower resistors in the voltage divider must also be considered.
  • #1
karumees123
1
0
Homework Statement
Need help finding the resistor size for circuit
Relevant Equations
Kirchhoff's Current Law
Ohms Law
1602533198476.png


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!
 

Attachments

  • 1602533193513.png
    1602533193513.png
    7.2 KB · Views: 132
  • 1602533195029.png
    1602533195029.png
    7.2 KB · Views: 119
Last edited:
Physics news on Phys.org
  • #2
karumees123 said:
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. :smile:

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?
 

1. What is Ohm's Law and how does it relate to finding resistor size for a circuit?

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points. In other words, as the voltage increases, the current also increases. This law is important in determining the size of a resistor needed in a circuit.

2. How do I calculate the resistor size using Ohm's Law?

The formula for Ohm's Law is V=IR, where V is voltage, I is current, and R is resistance. To calculate the resistor size, you will need to know the desired voltage and current for your circuit. Then, simply rearrange the formula to solve for R: R=V/I.

3. What units are used for the values in Ohm's Law?

Voltage is measured in volts (V), current is measured in amps (A), and resistance is measured in ohms (Ω). It is important to use consistent units in your calculations.

4. Can I use any resistor size in my circuit?

No, the resistor size you choose must be within the range of values available. Resistors come in standard sizes, so you may need to use a combination of resistors to achieve the desired resistance for your circuit.

5. Are there any other factors I should consider when choosing a resistor size?

Yes, in addition to the resistance needed, you should also consider the power rating of the resistor. This is the maximum amount of power the resistor can safely handle without overheating. Make sure to choose a resistor with a power rating that is equal to or greater than the power in your circuit.

Similar threads

Engineering Calculating the voltage at a certain Resistor
    • Engineering and Comp Sci Homework Help
Replies
3
Views
808
Engineering Unknown resistor in a series-parallel circuit
    • Engineering and Comp Sci Homework Help
Replies
17
Views
9K
Engineering Why are the voltages calculated in this way? (CE BJT Amp circuit)
    • Engineering and Comp Sci Homework Help
Replies
8
Views
1K
How to find the equivalent resistance of this electric circuit?
    • Engineering and Comp Sci Homework Help
Replies
5
Views
3K
Ohm's Law - Finding Source Voltage
    • Introductory Physics Homework Help
Replies
3
Views
527
Calculating the voltage in an OP-amp circuit with a current source
    • Engineering and Comp Sci Homework Help
Replies
1
Views
992
Calculating R1 and R2 for Opto-Triac Output Circuit
    • Engineering and Comp Sci Homework Help
Replies
34
Views
4K
Engineering Simplifying a series / parallel circuit and calculating unknown values
    • Engineering and Comp Sci Homework Help
Replies
3
Views
1K
Finding current in the 25 ohm resistor
    • Engineering and Comp Sci Homework Help
Replies
6
Views
3K
Finding average current through resistors R1 and R2
    • Engineering and Comp Sci Homework Help
Replies
11
Views
2K

Hot Threads

Recent Insights

Back
Top