Electrical current, often simply called “current,” is the movement of electric charge. It’s measured in units called amperes (A). Just as water flows from a higher to a lower point, conventionally electric current flows from areas of higher electric potential (+ terminal) to lower potential (- terminal). However, the actual charge carriers, electrons, move from the negative terminal to the positive terminal.
We deal with electrical current every day of our lives. For household appliances to work, there must be an orderly movement of charge carriers from one point to another. This is the simplest definition of electrical current. But before understanding how the movement of these charges occurs, it’s important to familiarize yourself with some concepts.
Let’s start by explaining how circuits work. Think of electrons scattered across the surface of any object (example copper wire which is conductor). Without some external influence, these electric fields result in a disordered movement of charges.
Now things change when we introduce a force into the circuit (potential difference). In this case, the most common way is to place a battery in the circuit. This generates an electric field around the circuit (conductor), resulting in an orderly flow of charge carriers, creating an electrical current. In this case, we say the electric field is non-zero.
MATHEMATICAL CURRENT INTENSITY AND FLOW
It is possible to calculate the current intensity using the formula where the amount of charge passing through a plane over a time interval, ∆t, is considered. Pay attention to the units of measurement for each order of magnitude. The convectional current direction within a circuit is always from higher potential to lower potential. Don’t forget this, as it is very important.
i – Electric current in Ampere [A]
Δq – Change of charge during time (final value – initial value) in Coulomb [C]
Δt – Change in time (final time – initial time) in seconds [s]
Not all circuits are circular, their shapes can vary greatly. In these cases, Kirchhoff’s Law comes into play. This concept helps us understand the principle of conservation. The sum of currents entering a node must equal the sum of currents leaving the same node. To calculate the total current value, it’s simple. Just add up the values of each branch of the current to know the total: Ia = Ib + Ic.
So, the total current flowing from the battery will be divided between the two branches in the circuit. A similar thing happens with the flow of water because it also branches into water pipes in a similar way. The simulation results confirm Kirchhoff’s law:
REAL AND CONVENCTIONAL FLOW OF ELECTRONS
Ordered electrons follow in a specific direction within the circuit, which can be either real or conventional. This means that the conventional direction of current is the direction in which positive charge carriers would move, even though the actual charge carriers are negative (electrons).
CONVENTIONAL FLOW OF ELECTRONCS
REAL FLOW OF ELECTRONCS
How do electrons move from one potential to another? Simple. Through electrical wires. And this brings us to resistance and resistivity. Wires conduct electrical current, but depending on the material of the conductor, the electric charge can be affected in some way.
In reality, conductive wires offer resistance to the passage of current, as there are constant collisions between electrons and the atoms that make up the wire material, generating heat. This process is also known as the Joule effect.
SHORT CIRCUIT
If copper, aluminum, or any other metal is connected directly to two battery terminals, as in the circuits above, a large current can flow because the conductor has low resistance. The image below shows the simulated value of the current that flows in this circuit.
This connection is called a short circuit, which occurs when there is a low-resistance connection between two points in an electric circuit, allowing a large amount of current to flow through the circuit. This high current can cause excessive heat generation, leading to component damage, fires, or even explosions.
In order to avoid the dangers of a short circuit, a fuse should be used to break this low-resistance connection, stopping the current flow.
TYPES OF ELECTRICAL CURRENT
DIRECT CURRENT (DC)
Direct Current flows in one direction, much like water moving steadily through a pipe. Batteries and most electronic devices use DC because it’s stable and easy to control. For example, smartphones and portable electronics rely on DC power from batteries.
ALTERNATING CURRENT (AC)
Alternating Current reverses direction periodically, similar to the back-and- forth motion of ocean waves. AC is used in homes and businesses for powering appliances and lighting. It’s generated by power plants and distributed through power lines. The frequency of AC in most countries is 50 or 60 cycles per second (Hertz), which determines how often the current direction changes.
UNDERSTANDING ELECTRIC CIRCUITS
Electric current flows through complete circuits. A circuit is a closed loop or path through which electricity can flow. It typically includes a power source (like a battery or outlet), conductors (wires), and components (such as resistors, capacitors, and lights). For current to flow, there must be a complete path without interruptions.
REAL-WORLD ANALOGIES
Analogies can help visualize electrical current:
Water Flow: Just as water flows through a hose when a valve is opened, electrical current flows through a wire when there’s a complete circuit. The amount of water flowing through the hose can be compared to the amount of current flowing through a wire.
Traffic: Imagine cars flowing along a highway. The number of cars passing a point per second is like the current in a circuit. The speed of the cars can be analogous to the voltage.
VOLTAGE AND CURRENT RELATIONSHIP
Voltage (electric potential difference) is what causes electric current to flow. It’s similar to the pressure that pushes water through a pipe. When there’s a higher voltage difference between two points in a circuit, more current flows. This relationship is described by Ohm’s Law, which states that current (I) equals voltage (V) divided by resistance (R):
I – Electric current in Ampere [A]
U – Voltage (potential difference) in Volt [V]
R – Electric resistance in Ohm [Ω]
SAFETY CONSIDERATIONS
Electricity must be handled with care due to its potential dangers. Always follow safety guidelines and avoid contact with live wires or electrical devices when wet. Electrical shocks can occur even at low voltages, especially if conditions are wet or if the current passes through vital organs like the heart.
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