If I have a one volt D.C. battery and a resistor of .0005 ohms, is the current really 2,000 amps? Like enough to kill someone

Question

If I have a one volt D.C. battery and a resistor of .0005 ohms, is the current really 2,000 amps? Like enough to kill someone.

Answer 1

If you have a voltage source of 1V and the circuit has a resistance of 0.005 ohm, then indeed you will run 2000A through the circuit. But there are caveats

• Most voltage sources are not ideal. They are modeled as having an "internal resistance" which is part of the circuit if they are part of the circuit. For an AA battery, it is on the order of 0.5 ohms. So you can't use a AA in the circuit the way you want... the result would be a circuit reistaance of 0.5005 ohm or something like that. And if you short the circuit like this, it is highly likely that you will start to push against kinematic limits of the reactions in the battery, and the voltages will dip, rather than being held constant at 1V.
• Wires that carry large amperage heat up. As conductors heat up, their resistance increases. This is the fundamental way lightbulbs work. When you turn them on, their resistence is very low, so a lot of current flows. This heats the filament up until there is a balance between the power being put into the filament and the power dissipated as heat.

That being said, what you describe is exactly how MIG welding works. A MIG welder typically outputs something on the order of 12V, but a large number of amps.

Answer 2

That would be the current in the circuit created by the .0005 Ohm resistor and the 1 volt battery, yes, but only within that circuit. In order for a 1 Volt battery to result in 2,000 amps of current through a human body, the human body would need to also have a resistance of .0005 Ohms.

Answer 3

There are really three separate issues here.

1. How much current the battery can actually deliver. All real batteries have internal resistance. You would have to know what the internal resistance of the one volt battery is. Then you need to add that to the load resistance of .0005 Ohms and divide the battery emf (open circuit voltage) by the total to get the maximum possible current to the load. That current may only exist for a short period of time. For example, a lead acid car battery can deliver several hundred amps to a short circuit for a brief period of time.

2. To determine how much current the battery can deliver to the body, you need to know the body's resistance. At low voltages the body resistance is quite high under dry contact conditions, on the order of thousands to 10's of thousands of Ohms. So even if the battery had zero internal resistance, for a 1 volt battery we are talking about hundredths or thousandths of a milliampere. Way below that needed for a lethal electric shock

3. If a battery were to harm someone, it generally wouldn't be due to the battery delivering current through the body, since as already noted the current through the body would typically be very small due to the high resistance of the body. Injuries from high battery currents typically are due to touching a metal part that shorts the battery terminals. In other words, the injury would be burns due to touching metal that is hot because of resistance heating. In the safety business we call these "energy hazards" to differentiate them from "electric shock hazards". While severe burns can occur, the injury is not likely to be fatal. Fatal electric shock requires current through the heart generally requiring a higher voltage source of sufficiently low source impedance. Moreover, the vast majority of electric shocks involve ac sources, not dc.

Hope this helps.