4 Ways to Calculate Total Current

2024 Author: Samantha Chapman | [email protected]. Last modified: 2024-01-15 13:47

The simplest way to represent a series of connections in a circuit is a chain of elements. The elements are inserted sequentially and on the same line. There is only one path on which electrons and charges can flow. Once you have a basic idea of what a series of connections in a circuit implies, you can understand how to calculate the total current.

Steps

Method 1 of 4: Understand the Basic Terminology

Step 1. Familiarize yourself with the concept of current

Current is the flow of electric charge carriers or the flow of charges per unit of time. But what is a charge and what is an electron? An electron is a negatively charged particle. Charge is a property of matter that is used to classify whether something is positive or negative. As with magnets, the same charges repel each other, the opposite ones attract.

• We can explain it using water. Water is composed of molecules, H2O - which stands for 2 atoms of hydrogen and one of oxygen linked together.
• A running watercourse is made up of millions and millions of these molecules. We can compare the flowing water to the current; molecules to electrons; and the charges to the atoms.

Step 2. Understand the concept of voltage

Voltage is the "force" that makes the current flow. To better understand the voltage, we will use a battery as an example. A series of chemical reactions take place inside a battery that create a mass of electrons at the positive end of the battery.

• If we connect the positive end of the battery with the negative one, through a conductor (eg. A cable), the mass of electrons will move to try to move away from each other, for the repulsion of the same charges.
• Furthermore, due to the law of conservation of charges, which says that the total charge in an isolated system remains unchanged, the electrons will try to pass from the maximum negative charge to the lowest possible one, thus passing from the positive pole of the battery to the negative one.
• This movement causes a potential difference between the two extremes, which we call voltage.

Step 3. Understand the concept of resistance

Resistance, on the contrary, is the opposition of certain elements to the flow of charges.

• Resistors are elements with a high resistance. They are placed in some points of the circuit to regulate the flow of electrons.
• If there are no resistors, the electrons are not regulated, the device may receive too high a charge and be damaged or catch fire due to too high a charge.

Method 2 of 4: Finding the Total Current in a Series of Connections in a Circuit

Step 1. Find the total resistance in a circuit

Imagine a straw you are drinking from. Pinch it several times. What do you notice? The water flowing through it will decrease. These pinches are the resistors. They block the water which is the current. Since the pinches are in a straight line, they are in series. In the example image, the total resistance for series resistors is:

• R (total) = R1 + R2 + R3.

  

  Step 2. Identify the total voltage

  Most of the time the total voltage is provided, but in cases where individual voltages are specified, we can use the equation:

  • V (total) = V1 + V2 + V3.
  • Why? Using the comparison with the straw again, after having pinched it, what do you expect? You have to make more effort to let the water pass through the straw. The total effort is the sum of the efforts you have to put in to get through each pinch.
  • The "force" you need is the voltage, since it causes the current or water to flow. Therefore it is logical that the total voltage is the sum of those required to cross each resistor.

  

  Step 3. Calculate the total current in the system

  Using the comparison with the straw, even in the presence of pinches, is the amount of water you receive different? No. Even if the speed with which the water arrives varies, the amount of water you drink is always the same. And if you consider more carefully, the amount of water that enters and leaves the pinches is the same given the fixed speed with which the water flows, so we can say that:

  I1 = I2 = I3 = I (total)

  

  Step 4. Remember Ohm's Law

  Don't get stuck at this point! Remember that we can consider Ohm's law that binds voltages, current and resistance:

  V = IR.

  

  Step 5. Try to work with an example

  Three resistors, R1 = 10Ω, R2 = 2Ω, R3 = 9Ω, are connected in series. To the circuit is applying a total circuit of 2.5V. Calculate the total current of the circuit. First calculate the total resistance:

  • R (total) = 10Ω + 2Ω + 9Ω
  • Therefore R (total) = 21Ω

  

  Step 6. Use Ohm's Law to calculate the total current:

  • V (total) = I (total) x R (total).
  • I (total) = V (total) / R (total).
  • I (total) = 2, 5V / 21Ω.
  • I (total) = 0.1190A.

  Method 3 of 4: Find the Total Current for Parallel Circuits

  

  Step 1. Understand what a parallel circuit is

  As its name indicates, a parallel circuit contains elements that are organized in parallel. This consists of several cable connections that create different paths where current can flow.

  

  Step 2. Calculate the total voltage

  Since we covered the terminology in the previous point, we can go straight to the calculations. Take as an example a tube that separates into two parts of different diameters. For the water to flow in both pipes, do you perhaps need to apply different forces on the two branches? No. You just have to apply enough force for the water to flow. So, using water as an analogy for current and force for voltage, we can say that:

  V (total) = V1 + V2 + V3.

  

  Step 3. Calculate the total resistance

  Suppose you want to regulate the water flowing in the two pipes. How can you block them? Do you place a single block for both tubes, or do you position several blocks in succession to regulate the flow? You should opt for the second choice. For the resistance it is the same. Resistors connected in series regulate much better than those placed in parallel. The equation of the total resistance in a parallel circuit will be:

  1 / R (total) = (1 / R1) + (1 / R2) + (1 / R3).

  

  Step 4. Calculate the total current

  Let's go back to our example of water flowing in a pipe that splits. The same can be applied to the current. Since there are several paths that the current can take, it can be said that it must be divided. The two paths do not necessarily receive the same amount of charge: it depends on the strength and materials that make up each branch. Therefore, the equation of the total current is equal to the sum of the currents flowing on the various branches:

  • I (total) = I1 + I2 + I3.
  • Of course, we can't use it yet because we don't own the individual currents. Again we can use Ohm's law.

  Method 4 of 4: Solve a Parallel Circuit Example

  

  Step 1. Let's try on an example

  4 resistors split into two paths which are connected in parallel. Path 1 contains R1 = 1Ω and R2 = 2Ω, while path 2 contains R3 = 0.5Ω and R4 = 1.5Ω. The resistors in each path are connected in series. The voltage applied on path 1 is 3V. Find the total current.

  

  Step 2. First find the total resistance

  Since the resistors on each path are connected in series, we will first find the solution for the resistance on each path.

  • R (total 1 & 2) = R1 + R2.
  • R (total 1 & 2) = 1Ω + 2Ω.
  • R (total 1 & 2) = 3Ω.
  • R (total 3 & 4) = R3 + R4.
  • R (total 3 & 4) = 0.5Ω + 1.5Ω.

  • R (total 3 & 4) = 2Ω.

    

    Step 3. We use the equation for parallel paths

    Now, since the paths are connected in parallel, we will use the equation for resistances in parallel.

    • (1 / R (total)) = (1 / R (total 1 & 2)) + (1 / R (total 3 & 4)).
    • (1 / R (total)) = (1 / 3Ω) + (1 / 2Ω).
    • (1 / R (total)) = 5/6.

    • (1 / R (total)) = 1, 2Ω.

      

      Step 4. Find the total voltage

      Now calculate the total voltage. Since the total voltage is the sum of the voltages:

      V (total) = V1 = 3V.

      

      Step 5. Use Ohm's Law to find the total current

      We can now calculate the total current using Ohm's law.

      • V (total) = I (total) x R (total).
      • I (total) = V (total) / R (total).
      • I (total) = 3V / 1, 2Ω.
      • I (total) = 2, 5A.

      Advice

      • The total resistance for a parallel circuit is always less than each resistance of the resistors.

      • Terminology:

        • Circuit - composition of elements (e.g. resistors, capacitors and inductors) connected by current-carrying cables.
        • Resistors - elements that can reduce or resist the current.
        • Current - flow of charges in a conductor; unit: Ampere, A.
        • Voltage - work done by electric charge; unit: Volt, V.
        • Resistance - measurement of the opposition of an element to the passage of current; unit: Ohm, Ω.