Electronic – High voltage, low current and vice versa

amperagebatteriescurrentohms-lawvoltage

Can someone please explain to me in simple terms how is it possible to have high voltage and low current and low voltage and high current and what actually does harm to human body.

Here is what I don't understand:

12V / 1000 Ohm = 0.012A (12mA)

300V / 1000 Ohm = 0.3A (300mA)

So if I go and touch 12V battery terminals, my body is 1000 Ohms 12mA of current flow through me and it is safe.

Then if I go and touch 300V battery terminals and 300mA of current flow through me it is fatal.

Yet 12V battery vehicles have fuses rated for 30A and more. Well, that means if there is a short etc. 30A will flow through a wire and break the fuse.

30A in a short circuit wire with a 12V is safe and 0.3A is a 300V is not? How is this possible?

Best Answer

First of all, 30A in a short circuit wire with 12V is not safe. Chances are the thing will go bang or get extremely hot before you even have the chance to touch it.

As for your actual question 'how is it possible to have high voltage and low current and low voltage and high current?'. That question you have sort of answered yourself. It's Ohm's Law. you have used the equations to work out the current in those batteries. Now, change the resistance in that circuit and you will see the voltage changes, hence that is how it is possible to have high voltage and low current, and also low voltage and high current.

As for what damage can these currents do to a human.... Well, this link HERE will tell you all you need to know about fatal currents and electrical safety. There is also a discussion on what damage can be done in a question asked on this site HERE if you wanted a bit more of a read!