Issue finding change in voltage across a resistor

AI Thread Summary
The discussion revolves around calculating the voltage drop across resistor R1 in a circuit with resistors R1, R2, and R3. The user initially calculates the total current as 0.015A using the equivalent resistance of 816Ω and a supply voltage of 12V. However, the voltage drop calculated across R1 is incorrect, as the assumption that all current flows through R1 is flawed. It is suggested that the user should draw the circuit with labeled voltages and currents for clarity. Understanding the current distribution in the circuit is essential for accurate voltage drop calculations.
Blakeasd
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Homework Statement



Determine the voltage drop across R1
R1 = 770 , R2 = 630 , and R3 = 470 .
The equivalent resistance is 816Ω

19-39alt.gif

Homework Equations



V = IR

The Attempt at a Solution



1.) I find the total current of the circuit:

V = IR -> I = V/R
I = 12v/816Ω = 0.015A

2.) I then find the voltage drop across that particular resistor:

V = IR
V = 0.015A * 770Ω
V = 11.32v

This has been confirmed to be the wrong answer.

I don't understand what I am doing incorrectly.

Could someone please help me understand my mistake (where ever it may be)?

Many Thanks!
 
Physics news on Phys.org
You need to draw the circuit with all of the voltages and currents labeled so that you can see clearly what is going on. Thinking that the 15ma all goes through R1 is incorrect.
 

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