Understanding Why My Charger Doesn't Electrocute Me
Introduction
Have you ever plugged in your phone or laptop charger and touched the charging end without experiencing a shock? If so, you're not alone, and there are several reasons for this phenomenon. Let's delve deeper into the science and engineering behind chargers to understand why they are designed to prevent harmful shocks.
Key Reasons for No Shock
When you touch the charging end of your charger while it is plugged into an outlet and don't receive a shock, it's likely due to a combination of factors including:
Insulation
Most chargers are designed with insulated materials that prevent electrical current from passing through to the user. The outer casing of the charger and the charging cable is typically made of non-conductive materials, such as plastic, which ensures that the user remains safe from electrical currents.
Low Voltage
The voltage at the charging end for devices like smartphones or tablets is much lower than the mains voltage. For example, USB chargers output 5 volts, which is not enough to cause a harmful shock. This low voltage, combined with the non-conductive materials used in the construction of the charger, minimizes the risk of an electrical incident.
Design Features
Many chargers have built-in safety features such as short-circuit protection and ground fault protection. These features help prevent any electrical faults that could lead to a shock. Short-circuit protection prevents the flow of excessive current, while ground fault protection ensures that any electrical leakage is quickly rerouted to the ground, reducing the risk of electrocution.
Proper Usage
Handling the charger correctly is also crucial. Avoid touching exposed wires and ensure that the charger is in good condition. If done properly, the risk of shock is significantly reduced. Additionally, always check the condition of your chargers and replace any that show signs of wear and tear.
Proper Grounding
Finally, if the charger is properly grounded and the outlet is functioning correctly, the risk of electrical shock is further reduced. Grounding ensures that any electrical current can flow to the ground, dissipating the risk of a harmful shock.
The Case of the Phone Charger with 5V DC
The lead on your phone charger transfers the 5 volts DC from the charger to your phone. This 5V DC is sufficiently low that it cannot develop a high enough current to cause damage, given the body's skin resistance is high enough. Skin resistance plays a crucial role in preventing electrical currents from reaching harmful levels.
Why a MacBook Charger Doesn't Electrocute You
Similarly, a MacBook charger used to charge the computer's battery does not pose a significant risk of electrocution even if the MacBook-end is placed on your thumb. Here are the key reasons:
The Output Voltage
Modern MacBook chargers generally output 19 volts. For many people, skin resistance is high enough to block the flow of current. Even if your skin resistance is low, the resulting shock would still be minimal, comparable to touching 9V battery terminals to your tongue to test its viability.
Cardiac Current Requirements
To be "electrocuted" as in death, it takes anywhere between 5mA to 100mA of current to flow through the heart. If you did manage to get current flow across the skin of your thumb, the electrical circuit would be completed far from your heart, making it irrelevant. If the circuit were completed, the body's natural resistance would block the low-voltage 19V from reaching your heart.
Conclusion
In summary, chargers are designed with a myriad of safety features to prevent harmful shocks. Understanding these features and practicing proper usage can further enhance your safety. Always ensure that your chargers are in good working condition and avoid touching exposed parts when they are plugged into the wall.