At some point in your life, you may find yourself in dire need to centrifuge baboon blood during a power outage. Time is sensitive, so waiting for power to return is not an option. Luckily, you have a solar-powered system with a 90Ah/12V deep-cycle battery connected to a 400W inverter. Unluckily, you’ve already burned out an inverter due to your ignorance about electricity. How do you know your only remaining inverter can handle the job?
The answer is absurdly simple. Just remember this equation from high school physics:
Watts (W) = Volts (V) x Amps (A)
The tag on the power cord tells you that the centrifuge draws up to 2.2 amps. The AC output on your inverter is 110 volts. Multiplying these two numbers tells you that the maximum power running through this system is about 242 watts, well under the 400W rating of your inverter.
This is good news, as you can now stop doing this.