Why Do The Positive And Negative Wires Spark When Touched?
When positive and negative conductors touch, it produces a spark. Same is the case when phase and neutral wires make a contact. This scenario is known as a short circuit, which occurs when an unintended connection is made between two points having different electrical potential.
In the case of a short circuit (when the positive ⨁ terminal of a battery makes contact with the negative ⊖ terminal or the phase wire touches the neutral wire), a high current starts to flow due to the potential difference between the two points. This high voltage ionizes the air between the two conductors. During the process of air ionization, molecules lose electrons, creating a hot, glowing, and electrically conductive plasma.
The free electrons are attracted to the positive ⨁ terminal, while the ions are attracted to the negative ⊖ terminal. During the transition of ions and electrons through the plasma, they collide with each other as well as with air molecules between the terminals. Heat and light are produced during these collisions, which is observed as a spark in the case of short circuits.
The intensity of the produced spark depends on the level of voltage and current. The higher the voltage or current flowing in the circuit, the stronger the spark that will be produced.
Let’s see why the spark ignite during the short circuit
- Electrical Potential Difference: Positive and negative wires represent different electrical potentials (voltages). Same is case in Phase and Neutral wire in AC circuits. When they touch and make a contact between these two wires, the high potential difference causes a large current to flow rapidly between them.
- Rapid Current Flow: The electrical current seeks the path of least resistance. When the wires touch directly, there is no resistance or electrical load between these two wires. Hence, they create a very low-resistance path, causing a sudden surge of current.
- Energy Release: The rapid current flow generates heat and light energy. The heat can be intense enough to ionize the air around the contact point, creating a visible spark.
- Material Properties: The materials of the wires (usually copper or aluminum) can vaporize at the point of contact due to the heat, contributing to the spark.
- Circuit Conditions: If the circuit is powered, especially with a significant voltage and current capacity, the energy released when the wires touch can be substantial, resulting in a larger spark.
For example:
Suppose a phase (hot) and neutral wire touch while they are supplied from a single-phase, 50kVA, 230V transformer. We know that theoretically, the voltage becomes almost zero in the case of a short circuit. If we assume the voltage to be 1V (to avoid an infinite value), the amount of current flowing between those two wires would be extremely high.
I = P ÷ V ….. (∴ P = V × I)
Where:
- I = Current in Amps
- P = Power in Watts
- V = Voltage in Volts
Putting the values:
Current in Amps = I = 50kVA ÷ 1V
Current in Amps = I = 50kA
This high amount of current will instantly start to flow between the two wires, which are not capable of handling such a current. Consequently, it will produce a high spark and flames, leading to damage to the connected appliances or even a hazardous fire if proper protective devices such as circuit breakers and fuses are not installed.
With proper protective devices in place, when the high current surge occurs, the breaker will detect the overload and disconnect the circuit from the fault.
The same scenario applies to capacitors and batteries, where positive and negative terminals accidentally or intentionally make contact. If the power rating is high, an intense spark will occur immediately.
Safety Concerns
- Fire Hazard: Sparks can ignite flammable materials.
- Equipment Damage: Short circuits can damage electrical components and devices.
- Personal Injury: Sparks can cause burns or electric shock.
Prevention
- Insulation: Ensure wires are properly insulated.
- Proper Connections: Use appropriate connectors and avoid loose wires.
- Circuit Protection: Implement circuit breakers or fuses to prevent short circuits.
Always handle electrical systems with care and ensure circuits are de-energized before working on them.
FAQ
Why do positive and negative wire spark when touched?
The spark is created by the ionization of the air between the wires. When the voltage between the wires is high enough, the air molecules become ionized, which means that they lose electrons. This creates a plasma, which is a hot, glowing gas that is electrically conductive. The plasma is what causes the spark
What happens when you touch a positive and negative wire?
We get shocked by being an integral part of a complete circuit where there is a significant voltage differential. If you touch the positive wire and then also touch the negative wire or neutral or ground with that differential, you will get shocked
Why would a wire spark?
Common Causes of a Sparking Electrical Outlet
Loose wiring – Wires that are loose or not properly connected can cause arcing and sparking. This is often because the wires aren’t correctly tightened when reinstalling an outlet or from wear and tear of the wire connection over time
What happens when two electrical wires touch?
Whenever two wires are at different voltages, current will pass between them if they are connected. Your body can connect the wires if you touch both of them at the same time. Current will pass through your body
What happens if you touch the positive and negative battery cables together?
If they were hooked directly to the battery, touching them together would only affect those wires by making them heat up a little. One thing you may want to do as a matter of course would be to perform a power down of the vehicle’s controllers
Why don’t we get shocked if we touch a wire?
If the absence of a ground connection means that there is zero potential difference between portions of a person’s body, no current will flow, and shock will not occur
What happens when a positive and negative charge touch?
Answer and Explanation:
When a positively charged object and a negatively charged objects come in contact with each other, the charge flow from the negative charged object to the low charged positive object until the charges on both the objects become equal
What happens if positive and neutral wires touch?
When live wire comes in contact with the neutral wire, then the insulation of wires is damaged or there is a fault in the appliance. In such a situation, the current in the circuit abruptly increases. This is known as short circuiting
