Electrical circuit porblem using ohms law

• Engineering
• babic
In summary, the problem requires using all of the given resistors (2 x 12 ohms, 2 x 24 ohms, and 2 x 36 ohms) to create a circuit with a total resistance of 4 ohms. The closest solution found was 3.9560 ohms, achieved by combining the resistors in various series and parallel configurations. There is no known trick or shortcut to solving this problem.
babic

Homework Statement

Using all the following resistors : 2 x 12 ohms , 2 x 24 ohms , and 2 x 36 ohms. create a circuit where the total resistance will be 4 ohms.

The problem states that I have to use ALL of the resistors..making it so complicated

Homework Equations

1/Req = 1/R1 + 1/R2 + 1/R3... (in parallel)
Req + R1+R2+R3... (in series)

The Attempt at a Solution

The closest I got was (1/12) + (1/(24+36)) + (1/36) + (1/12) + (1/24). Is there a trick or something..

I could have 4 parallel resistors.. 12 parallel to 12 parallel to 24 parallel to 24.
(1/24) + (1/24) + (1/12) + (1/12) = 1/4 ... but I did not use the 2 x 36 ohms.. help will be appreciated.

Welcome to PF;
I don't think there's a trick exactly - beyond understanding the problem.
i.e. since all the resistors are greater than 4ohms, you will need to combine a lot in parallel to reduce the overall resistance.

Also 12, 24, and 36, are all multiples of 4... your target resistance.

I guess you could design the circuit with a short circuit across unwanted resistors... but that is usually considered the same as not using them.

Hm ... I tried a few combinations and I can't get it either. My attempts were hardly exhaustive, but I sure don't see it.

3.9560Ω (the closest so far) is 4.0Ω rounded :)

Then there is the 12s and 24s in parallel, in series with the 36's in parallel - but short-curcuit the 36s :)

Since all values divided by 3 as well as 4 I figured looking at triples.
12 = 4x3x1
24 = 4x3x2
36 = 4x3x3

Then there is just trying every possible combination of series and parallel.
I don't think there would be more than two series sections... there won't be that many combinations.

Thank you guys, I'll just stick with the 3.9560ohms answer.

1. What is Ohm's Law?

Ohm's Law is a fundamental principle in physics that describes the relationship between voltage, current, and resistance in an electrical circuit. It states that the current flowing through a conductor is directly proportional to the voltage applied, and inversely proportional to the resistance of the conductor.

2. How do you calculate the voltage in an electrical circuit using Ohm's Law?

To calculate the voltage in an electrical circuit using Ohm's Law, you can use the formula V = IR, where V is the voltage in volts, I is the current in amperes, and R is the resistance in ohms. Simply plug in the known values and solve for V.

3. Can Ohm's Law be applied to all types of electrical circuits?

Yes, Ohm's Law can be applied to all types of electrical circuits, as long as they follow the basic principles of voltage, current, and resistance. However, it may not always be accurate in more complex circuits with non-linear components.

4. How does resistance affect the current in an electrical circuit?

Resistance is a measure of how difficult it is for current to flow through a conductor. According to Ohm's Law, as resistance increases, the current decreases, and vice versa. This means that a higher resistance will result in a lower current flow in the circuit.

5. Is Ohm's Law the only law that governs electrical circuits?

No, Ohm's Law is just one of the many laws that govern electrical circuits. Other important laws include Kirchhoff's Laws, which describe the conservation of charge and energy in a circuit, and Faraday's Law, which explains the relationship between magnetic fields and electric currents.

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