# Is a 2 Ampere power supply dangerous? [duplicate]

I'm sorry if this question seems extremly dumb or/and pathetic. I'm quite new to electronics. For one of my electronics projects, I want to buy a power supply like this one, but it says Output: 12V 2A and I know that 2 amps is dangerous for the human body. So what does it mean? Will I hurt myself if I touch the two cables or is it fine? I don't really understand this. I'm sure you all know the answer and if so, please explain why. Thank you!

EDIT: My question has been marked as a duplicate but it's different. The other question is about what voltages / currents are dangerous but I do now that. However, I'm asking if the 2A power supply always outputs 2 amps or if it is the maximum current it CAN output.

2A is the maximum current it can deliver.

It will always deliver 12V - as long as you don't put a load on it such that it would have to deliver more than 2A.

Then, the voltage will drop. Either because it over heats and burns out or because the engineer who designed made it so that it safely limits the current so as not to burn out and be a fire hazard.

The current that really flows depends on the resistance of the connected load and the voltage.

Ohms law says this E=IR, where E is voltage, I is current, and R is resistance.

It can be rewritten like this: I= E/R.

This is what we want, since it is the current that can kill you.

Your body can be thought of as a resistor. It has a resistance of several thousand ohms. It can vary from 1000 ohms to 100000 ohms.

Lets stick with the middle field: 10000 ohms.

I= E/R

I= 12/10000

I= 0.0012A

I=1.2mA

So, your power supply can deliver 2A, but it can only force 1.2 thousandths of an ampere through your body.

So, your powersupply is safe for you to use and to touch with your hands.

Always buy your power supplies from trustworthy sources. Switching power supplies must be properly made in order to isolate the ouput from the high voltage input.

A cheaply made powersupply might skimp on the isolation, and allow the output to be at a high voltage compared to the ground. There will be the rated voltage between the two output terminals, but the full line voltage between one of the outputs and ground. THAT can kill you, but has nothing to do with the rated output current or voltage. That kind of thing is poor design and manufacturing.

Power supplies are labelled with nominal voltage but maximum current. The current, up to the limit of the supply, is determined by the load. If you have no load (open circuit) you will get no current. Just like the many mains sockets in your house that don't have anything plugged into them, no current is flowing out of those sockets. If you connect a 1000 ohm resistor across a 12V supply you will get 12/1000 = 12mA flowing, which is less than the 2A that your supply can supply so the voltage will remain at 12V. If you reduce the value of the resistor, more current will flow, but when you get close to 2A, the voltage will fall towards 0.

You won't get 2A through your body from a 12V supply because of the resistance of your body.

Everything you need to know can be found here

This is one of many Youtube videos made by a real character who goes by the handle of ElectroBOOM. He clearly knows a good deal about safety, and is willing to bend the rules to the breaking point in order to both educate and entertain.

Another useful demonstration he provides is here. And yes, touching 120 VAC hurts. A bunch.

At about 1 minute into the video he applies 25 volts to his tongue with a 30 amp supply.

Just so you won't need to.

Product Safety is supposed to be by design and adherence to IEC Compliance and OEM company credibility to adhering to good safety designs.

If the company appears to have longevity and good standards, you can trust it is safe, but verify by looking for standards compliance specs. First impressions look ok for this LED driver. While Asian e-skateboard designs are not.

According to many lectures,
anything beyond 100mA can produce an hypothetical heartattack. beyond 300mA you can easily get molest superficial skinburns. and using switching powersupplies theoretically can really burn your fingers and salty skin beyond 300mA.
Thus. 2 ampere can be relatively dangerous (eventually not lethal) to a person depending if it's switching or not according to us.
Yes. 2A can damage skin and muscle and produce severe involuntary muscular movement and cause dramatic laboratory damage.

• And how do you expect a 12 volt powersupply to push 2A through the human body? – JRE Sep 8 '18 at 21:45
• at 12 volt is very unlikely dermal conductivity of a 'sweat' could be like an actual copper conductor but anyways you'd expect 1 amper easily flowing through your fingertip and thus if the current is switched not continous the current may increase to 2A thorugh your fingers or forearm as you expected like if it was any other electrolyte. i think – Diego Cadogan Sep 9 '18 at 0:13