5v 2.1 a意思

"5V 2.1A" is a description of the output specifications of a power supply or a charging device, typically found in USB chargers or power adapters. Here's what each part means:

• 5V: This is the output voltage. It means that the device is designed to provide a constant voltage of 5 volts. Voltage is a measure of electrical potential difference and is a crucial factor in determining the compatibility of a power supply with a device.

• 2.1A: This is the output current. It means that the device can supply up to 2.1 amperes of current. Current is a measure of the flow of electrical charge and is directly proportional to the power (watts) dissipated by a load.

When you connect a device that is compatible with these specifications to the power supply, it will receive 5 volts of voltage and up to 2.1 amps of current. The power (in watts) that the device receives is calculated by multiplying the voltage by the current:

Power (P) = Voltage (V) x Current (A)

For this example:

Power (P) = 5V x 2.1A = 10.5W

So, the device can provide up to 10.5 watts of power. This rating is important for ensuring that the device you're charging or powering doesn't receive too much or too little power, which could damage it or reduce its efficiency.