Finding current with parallel resistors

In summary, the total equivalent resistance for the circuit is 1.755 Ω and the current supplied by the battery is 3.988 A. The current through R2 is not provided in the given information.
  • #1
cm846
4
0

Homework Statement





R1 = 2 Ω R2 = 5 Ω R3 = 11 Ω R4 = 10 Ω V = 7 V

What is the current through R2?

Homework Equations



Req for parallel resistors: 1/Req = 1/R1 + 1/R2...
Req for series resitors: Req = R1 + R2...
Electric potential V = current I x resistance R
I have found that Req is 1.755 and the current supplied by the battery is 3.988.


The Attempt at a Solution



I tried taking the 3.988 x 3.33 (the Req for R2 and R4) which is 13.29V and since the voltage drop is the same for parallel resistors I then divided by the 5 ohms to get 2.658 amps but that's not right.
 

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  • #2
Welcome to PF!

cm846 said:
R1 = 2 Ω R2 = 5 Ω R3 = 11 Ω R4 = 10 Ω V = 7 V

I have found that Req is 1.755 and the current supplied by the battery is 3.988.

Hi cm846! Welcome to PF! :smile:

How did you get the 3.988? :confused:
 
  • #3
I just took the 7V divided by the Req of 1.755 to get 3.988
 
  • #4
But that would require the battery and the R2-R4 combination to be the only things in the loop. :wink:
 
  • #5
3.99 is the answer to the question "What is the current supplied by the battery?" so I guess I'm not sure how I'd find it any other way than the way I showed?
 
  • #6
Sorry, I mistook the 1.755 it for the R2-R4 Req.

I should have asked, where did the 1.755 come from?
 
  • #7
Thats ok. I got the 1.755 for the Req for the entire circuit: (R2) 1/5 + (R4) 1/10 = 1/Req which is 3.33 then I added R3. 11 + 3.33 = 14.33 then 1/14.33 + (R1) 1/2 = 1/Req which is 1.755.
 
  • #8
ah, got it …

that's the current through the battery itself …

but you need the current through the loop containing the battery and R2 R3 and R4. :wink:
 

Related to Finding current with parallel resistors

1. How do I calculate the total current in a parallel circuit with resistors?

In a parallel circuit, the total current is equal to the sum of the currents in each individual branch. This can be calculated using Ohm's Law (I=V/R) for each resistor and then adding the individual currents together.

2. What is the formula for finding the equivalent resistance in a parallel circuit?

The formula for finding the equivalent resistance in a parallel circuit is 1/R(eq) = 1/R(1) + 1/R(2) + ... + 1/R(n), where R(1), R(2), etc. are the resistances of each individual branch.

3. How does the total current change if one resistor is removed from a parallel circuit?

If one resistor is removed from a parallel circuit, the total current will increase because there is less resistance in the circuit. This can be seen in the formula for calculating total current (I=V/R), where a decrease in resistance will result in an increase in current.

4. What happens to the total current in a parallel circuit if the voltage is increased?

If the voltage is increased in a parallel circuit, the total current will also increase because there is more potential difference pushing the current through the circuit.

5. Can the total current in a parallel circuit ever be greater than the individual branch currents?

No, the total current in a parallel circuit will always be equal to or less than the individual branch currents. This is because the total current is the sum of the individual branch currents and there is no way for the total to be greater than the sum of its parts.

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