# Tag Info

4

A permanent magnet has an associated magnetic field (obviously). What is not as obvious is that the magnetic field has an energy density which is proportional to $B^2$. When two magnets are aligned such that their magnetic fields are in the opposite direction then the energy in the field is reduced. This leads to a force (opposites attract) which can do work....

3

Among other things it violates conservation of energy. Generating a current requires you to push the electrons in the part of the wire that's near to you into their neighboring electrons, which then must push into their neighbors, all the way down the line. Obviously the electrons at each stage resist this due to repelling charges, so you need to do work ...

3

You can for a short time, but not permanently. Energy is conserved. It can change from one form to another, but you can't create it or destroy it. Potential energy is is one form of energy. Kinetic energy is another. An electric current is moving electrons. It also contains a form of energy. Suppose you have two magnets separate by a short distance. One is ...

2

The magnetic field caused by a magnet, like an electric field caused by charge and a gravitational field caused by mass, can only store energy. They can't create energy. The magnetic field can convert mechanical energy to electrical energy, but it requires a mechanical energy input. An example is moving a magnet through a coil of wire, or moving a coil of ...

2

A voltage can be induced in a conductive loop only if the magnetic flux through the loop changes. This can be done by a) a moving magnet or b) if you move the conductive loop which can't be done without some input energy.

1

In a circuit like you show, with a resistor connected to a power source by relativity short pieces of copper wire, the resistance of the wires is very small compared with that if the resistor, and the voltage drop across a segment of the wire would be close to zero. Most of the voltage drop occurs across the resistor.

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