What Causes High Current In Electricity?

Electric current is the flow of electric charge in an electrical conductor. It is measured in amperes (A), which indicates the amount of electric charge flowing past a point in the circuit per second. In simple terms, electric current is the rate at which electricity moves through a wire or device.

High current refers to a larger than normal amount of current flowing through a circuit. While some amount of current flow is necessary for electrical devices to operate, too much current can be dangerous and cause damage due to overheating. Understanding what causes high current and how to prevent it is important for electrical safety.

This article will examine the main factors that contribute to high current in electrical systems. Controlling these factors is key to avoiding potential hazards like blown fuses, tripped circuit breakers, fires, and shocks. We’ll also look at strategies to identify and mitigate sources of excessive current draw in your home or workplace wiring.


Voltage is the force that pushes electric current through a circuit. It is measured in volts. Voltage is generated by power sources like batteries or generators. When voltage is applied to a circuit, it gives electrons the energy they need to move through the wires and other conductive components.

Higher voltage levels allow more current to flow in a circuit. This is because higher voltage provides greater electromotive force to move the electrons. For example, a 9V battery can move more electrons through a circuit than a 1.5V battery, resulting in higher current.

The relationship between voltage (V), current (I), and resistance (R) is described by Ohm’s Law: V = I x R. For any given resistance, increasing the voltage will lead to a proportional increase in electric current.

Extremely high voltages can cause dangerously high currents that heat up wires and components. Fuses, circuit breakers, and other protection mechanisms are used to limit excessive current flow due to high voltage.


Resistance is one of the key factors that determines how much electric current flows in a circuit. Resistance essentially measures how much a material opposes the flow of electric current. Materials with lower resistance allow electric current to flow more freely, while materials with higher resistance impede electric current.

According to Ohm’s law, current is inversely proportional to resistance. This means that for a given voltage, lower resistance leads to higher electric current. When resistance is low, electrons can flow freely across the circuit resulting in greater current flow. On the other hand, higher resistance limits current flow even if the voltage remains constant.

Materials like copper have very low resistance, which allows them to readily conduct electricity and produce high current. Insulating materials like plastic have extremely high resistance and severly limit electric current. Therefore, choosing conductive materials with low resistance is an effective way to maximize current in an electrical system.

In summary, resistance directly affects how much current flows in a circuit. Lower resistance allows more current to flow when voltage is constant. High current results when resistance within a circuit is low.

Short Circuits

A short circuit occurs when two nodes of an electrical circuit are accidentally or intentionally connected together to create a low-resistance path for current flow. This results in excessive electric current between the nodes due to the minimal resistance in the circuit.

short circuits can cause high current due to low resistance path.

In a short circuit, the positive and negative terminals of a voltage source like a battery or power supply are connected by a conductor with little to no resistance. This provides an easy path for current to flow, since current always takes the path of least resistance according to Ohm’s law. The lower the resistance, the higher the current that will flow.

For example, if you were to take a wire and connect the two terminals of a 9V battery directly together, this would create a short circuit. The very low resistance wire allows a huge current to flow, much higher than if the battery was powering a normal resistive load like a light bulb or resistor. This excessive current flow can generate a large amount of heat rapidly and cause damage to the battery and wiring.

Short circuits are dangerous because the high currents can quickly lead to overheating and fire hazards. Fuses and circuit breakers are designed to detect short circuits and automatically open the circuit to stop the excessive current flow before major damage occurs.

Parallel Circuits

Current divides in parallel circuits when there are multiple branches for current to flow through. This allows more total current in the overall circuit compared to a single series path.

In a parallel circuit, each branch has its own path for current to flow. The total current in a parallel circuit is equal to the sum of the currents through each individual branch. So if there are three branches in parallel with currents of 1 amp, 2 amps, and 3 amps respectively, the total current in the parallel circuit is 1 + 2 + 3 = 6 amps.

This is different from a series circuit, where current can only flow through one path, so there is less total current. In a parallel circuit, each branch gets an equal voltage, and the resistance of each branch determines the current in that branch according to Ohm’s Law (Current = Voltage / Resistance).

The fact that current divides and flows through multiple paths is what allows parallel circuits to have a much higher total current capacity compared to series circuits. This is why wiring in homes and appliances is done in parallel – it allows more power to be delivered while using the same voltage.

Faulty Wiring

Faulty or improper wiring is a common cause of high electrical current. Wires inside walls and appliances can become damaged over time due to wear and tear, rodents chewing on wires, old age, corrosion, or incorrect installation. This damage results in loose connections, exposed wires, and conductors touching each other.

When wiring insulation breaks down, it creates opportunities for phase-to-phase or phase-to-neutral short circuits. Bare wire surfaces that touch can allow current to flow directly between conductors without passing through proper circuits. This creates unwanted paths for electricity to flow that were not part of the intended design.

Faulty wiring often leads to arcing, where electricity jumps across gaps in damaged insulation. Arcing generates a great deal of heat and can start electrical fires inside walls and equipment. It also allows large amounts of current to flow to places it is not supposed to go.

Outdated wiring that cannot safely handle modern electrical loads is another common issue. Older homes may have insufficient wire gauge or circuits rated for lower amperages than what is plugged into them. Drawing too much current through undersized wiring creates resistance that can overload circuits.

Proper installation by a licensed electrician and regularly inspecting wiring for damage, especially in older homes, helps prevent hazardous faults. Circuit breakers and ground fault circuit interrupters (GFCIs) can also shut off power automatically when abnormal current flows are detected.


Overloading circuits by plugging in too many devices is a common cause of high electrical current. Most household circuits are designed to handle 15-20 amps safely. When the cumulative draw of all connected devices exceeds this rating, it creates an overload condition.

Each electrical device draws a certain amount of current based on its wattage rating. For example, a typical hair dryer may draw 15 amps, while a phone charger only draws 1 amp. Individually, these devices stay within safe levels. But when multiple high-wattage appliances like dryers, heaters, microwaves etc. are powered on together, the total current quickly adds up.

The circuit breaker or fuse is supposed to trip and cut power if the current exceeds safe levels. But sometimes they can fail to act fast enough, allowing dangerously high current to flow for a sustained period. This causes the wires to overheat, creating a fire hazard. It can also damage connected appliances and electronics.

To prevent overloads, pay attention to your circuit’s amperage capacity and avoid plugging in more devices than it can handle safely. Use power strips with built-in circuit breakers to add extra protection against overloads. And spread high-wattage devices across multiple circuits whenever possible.

Damaged Devices

Damaged or faulty electrical devices and appliances can often draw excessive current and lead to electrical issues. This is because the internal components and wiring in the device can become compromised, causing short circuits or abnormal current flows. Here are some ways damaged devices can contribute to high current:

  • Loose, frayed or damaged power cords – This exposes the internal wires, allowing electricity to arc across gaps in the insulation. The exposed wires can also make contact with other conductive materials, shorting out the circuit.

  • Broken or cracked insulation – Similar to damaged cords, if the insulation within a device cracks or breaks down, it can lead to exposed conductors making contact and shorting out.

  • Internal short circuits – If components inside the device fail, such as burnt out resistors or transformers, it can create a dead short path for electricity to flow through.

  • Compromised safety cut-offs – Many devices have internal fuses or breakers that are designed to cut power if current gets too high. If these fail, excessive current will continue to flow.

  • Ground faults – Sometimes a hot conductor inside a device can make contact with the metal chassis. This provides a path directly to ground, bypassing the normal load and increasing current draw.

  • Damage from power surges – Large voltage spikes can blow out components and insulation inside a device, degrading its ability to safely regulate current flow.

In summary, any internal damage that allows conductors to make abnormal contact can lead to uncontrolled current flows and excessive electrical draw in a device.

Power Surges

Power surges, also known as voltage surges, are temporary increases or spikes in the voltage level in an electrical circuit. This sudden increase in voltage can lead to a corresponding increase in electric current in accordance with Ohm’s Law. There are a few reasons why power surges commonly occur:

  • Lightning strikes – If lightning directly strikes a power line or something connected to the power grid, it can induce a massive surge that propagates through the system.
  • Faulty wiring – Things like loose connections, frayed wires, or inadequate insulation can cause surges as arcs are generated.
  • Damaged transformers – If a transformer in the power grid is damaged, it can cause abnormal spikes in voltage.
  • Short circuits – When a short circuit occurs, it creates a huge drop in resistance which leads to an exponentially higher current. This may be preceded by a voltage spike.
  • Switching on heavy loads – The sudden inrush of current required to power ON big loads like air conditioners can cause a voltage drop which could create a surge when equilibrium is regained.

These sudden spikes in voltage can be very brief, often lasting less than a few microseconds. But in that moment, the higher voltage can generate significantly more current flow according to Ohm’s Law. Sensitive electronics may be damaged if they are not protected against these current surges. The transient nature and unpredictability of power surges makes them difficult to prevent completely. Good surge protection devices are necessary for protecting equipment.


In summary, high current in electrical systems is caused by several key factors. Low resistance, short circuits, faulty wiring, overloaded circuits, damaged devices, and power surges can all lead to dangerously high currents. Understanding the relationship between current, voltage, and resistance is essential. Being aware of potential causes and taking preventative measures such as proper wiring, circuit protection devices, and surge protectors can help avoid hazardous high current situations. Properly sizing wires, circuits, and overcurrent devices for the expected loads is also important. High current can result in circuit and equipment damage, overheating, fires, and shock/electrocution hazards. By educating ourselves on the causes and prevention of high electrical currents, we can work safely with these powerful systems.

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