[colug-432] Power Suppies: Voltage and Current

[jep200404 at columbus.rr.com]

On Thu, 23 Feb 2012 15:50:49 -0600, Thomas Cranston <thomas.w.cranston at gmail.com> wrote:

> I have wondered if too much amperage is bad. For example, I have 200
> amp service to my house, but it does not burn out my 35 watt light
> bulb. 

The 200 Amps is the _maximum_ that the service can handle. 
Likewise the amperage listed on power supplies is the 
maximum current it can deliver _at_the_rated_voltage. 
Likewise the amperage listed on devices is 
the highest current it will ever use. 

So you can hook up a 12 V device that uses 1 amp 
to a 12 V car battery that can deliver 700 amps, 
and the 12 V device is just fine. 

So here's what one looks for to match power supplies and devices. 

Voltage: Power supply voltage and polarity must be same as of device. 
Current: Power supply current must be at least as much as device's 
maximum. Power supplies that can deliver more current than needed 
are OK.