## How does running current through a coil cause a magnetic field?

#### How does running current through a coil cause a magnetic field?

Electricity and magnetism are interrelated in a great many ways. At the very basic levels, they are manifestations of the same fundamental physical concepts. As a result, electricity can produce magnetism and magnetism can produce electricity. One way in which electricity can produce magnetism is for charged particles to move. When an electric current passes through a coil (or any wire, for that matter), it creates a magnetic field. The coil develops a north magnetic pole and a south magnetic pole. I can’t really explain why because the answer is simply that moving charges create magnetic fields; that’s the way our universe works and no one has ever seen otherwise.

## If magnetic trains are to work, wouldn’t friction on the bottom of the train cre…

#### If magnetic trains are to work, wouldn’t friction on the bottom of the train create thermal energy which would destroy the magnetism of the train?

When a magnetically levitated train is operating properly, it doesn’t touch the track and experiences no friction. In principle, it shouldn’t get hot at all. The magnetic drag effect will warm the track slightly, but that won’t matter to the train’s magnets. Actually, the train’s magnets will almost certainly be superconducting wire coils with currents flowing in them. That type of magnet doesn’t depend on the magnetic order of permanent magnets. It’s the magnetic order of permanent magnets that is destroyed by heat. An electromagnetic coil will stay magnetic as long as current flows through it, even if it’s so hot that it’s ready to melt.

## If you have more volts is it more energy (like a stun gun

#### If you have more volts is it more energy (like a stun gun—is it better to have one with more current or volts or both)?

Volts is a measure of energy per charge. Thus if you tell me how much charge you have and the voltage of that charge, I can tell you have much energy that charge contains. I simply multiply the voltage by the amount of charge. Current is a measure of how many charges are moving through a wire each second. If you tell me how much current a wire is carrying and for how long that current flows, I can tell you how much charge has gone by. I just multiply the current by the time. To figure out how much energy electricity delivers to something (such as a person zapped by a stun gun), I need to know the voltage, the current, and the time. If I multiply all three together, the product is the energy delivered. In a stun gun, the voltage is important because skin is insulating and it takes high voltage to push charge through skin and into a person’s body. But current is also important because the more charge that passes by, the more energy it will carry. And time is important because the longer the current flows, the more energy it delivers. So all voltage and current are both important. I can’t guess which one is most important.

## What is the dangerous part of electricity: charge, current, voltage, or what?

#### What is the dangerous part of electricity: charge, current, voltage, or what?

Current is ultimately the killer. A current of about 30 milliamperes is potentially lethal when applied across your chest. But your body is relatively insulating, so sending that much current through your chest isn’t easy. That’s where voltage comes in. The higher the voltage on a wire, the more energy each charge on the wire has and the more likely that it will be able to pierce through your skin and travel through your body. Thus it’s a combination of voltage and current that is dangerous. Current kills, but it needs voltage to propel it through your skin.