Wired Charging
In batteries, a galvanic chemical reaction occurs and converts chemical to electrical energy until it has gone to completion, which powers the battery and device. When it does go to completion, the battery can no longer be used. However, in rechargeable batteries, which are found in many electronics (phones, laptops) and also can be bought, the charger can provide a current (and thus a voltage) which allows for the electrolytic reverse reaction to occur. This reverses the reaction and brings the battery back to the original. Now, the spontaneous reaction can continue to power the battery and device. This is known as recharging the battery.
iPhones, one of the most popular devices (and one of the more expensive common devices) in the U.S. today, have rechargeable batteries, like most smartphones. However, these smartphones, being incredibly thin, cannot be powered by AA or even AAA rechargeable batteries since they would be too thick for the device (a AA is 14.2 mm i diameter, and a AAA battery is 10.5 mm in diameter, but an iPhone 4S is a mere 9.3 mm thick - and newer models like the 5 and 5S are even thinner). These devices use rechargeable batteries, and have either a microUSB (non-Apple) or a 30-pin or Lightning (8-pin) adapters (for Apple devices) which connects into the bottom of the phone at one end and either a computer or wall adapter in the other. This charges the phone.
In the twenty-first century, charging is something that now we experience daily. Every day, we take our phones and plug them into the chargers to let them juice up for the next day. However, it is actually more complex that we had thought. Although there are many different ways that chargers charge devices, we, both owners of iPhones, decided to focus on Apple's connectors and adapters.
iPhones, one of the most popular devices (and one of the more expensive common devices) in the U.S. today, have rechargeable batteries, like most smartphones. However, these smartphones, being incredibly thin, cannot be powered by AA or even AAA rechargeable batteries since they would be too thick for the device (a AA is 14.2 mm i diameter, and a AAA battery is 10.5 mm in diameter, but an iPhone 4S is a mere 9.3 mm thick - and newer models like the 5 and 5S are even thinner). These devices use rechargeable batteries, and have either a microUSB (non-Apple) or a 30-pin or Lightning (8-pin) adapters (for Apple devices) which connects into the bottom of the phone at one end and either a computer or wall adapter in the other. This charges the phone.
In the twenty-first century, charging is something that now we experience daily. Every day, we take our phones and plug them into the chargers to let them juice up for the next day. However, it is actually more complex that we had thought. Although there are many different ways that chargers charge devices, we, both owners of iPhones, decided to focus on Apple's connectors and adapters.
How an iPhone Wired Charger Works
The mechanism for a iPhone charger produces a continuous power of 5 watts, which is what the standard power an iPhone uses to charge. It has a current of 1.0 amperes, which by the equation P = IV gives its voltage to be 5 V.
The mechanism that does this in the charger is far more complex than most people think. It has the current go through the circuit and converts the voltage essentially by turning the charger on and off 70000 times per second. This process is done by having a component that continually turns off and on paired with a converter which converts the current fragments to fragments with low voltage. These fragments then go through a separate component that converts it to a smooth continuous current with a voltage of 5 V. Although it seems very complicated, this process is extremely efficient and eliminates a lot of excess heat energy that is wasted in conventional charging (conventional charging typically has much higher voltage and current, and only now exceeds 90% efficiency). |
Apple's devices use a 5 W power adapter that has a current of 1.0 A and voltage of 5 V to charge.
PHOTO COURTESY OF: store.apple.com |
The Physics Behind It?
Primarily, we can see that the charger does still follow the equation for electrical power, P = IV (5 = 1*5). Frankly, there is not as much physics behind how wired chargers work, but more about the mechanical engineering aspect of it. For our project, more of the physics learning and applications came during the research of wireless/inductive charging and the creation of our own charger (please see next two pages); however, we did learn how wired charging works during our project and it was fascinating to think that the charger is turned on an off 70000 times per second.