What exactly produces fields? A question concerning Mechanics and Electrons

[flyingpig]

Homework Statement

I have two conceptual problems, they will relate to each other soon

1) Subatomic particles such as electrons, can they only have motion under the presence of an electric field? Humans have mass and charge, but we don't need to move under only the influence of E-fields right? In fact we can move even without G-fields. So how come electrons can only move under the presence of a E-field?

2)What exactly produces fields? For instance the Earth produces a G-field that is radially inward. But is the Earth as whole that produces this field or is it the center of mass of the Earth that is producing the field? Newton argued that if a body is inside a hollow spherical planet there is no Gravity inside that body will experience a net force of 0*, but does that mean there is no G-field then? Is the G-field of a hollow planet then produced by the surface of that planet?

* I am also assuming the body can still move around under constant speed?

 

[flyingpig]

Am I right or is this complete garbage?

 

[L-x]

Electric fields may accelerate charged subatomic particles (such as electrons) as may gravitational fields, but neither need be present for the particle to be moving. Be careful to make sure you understand the difference between something causing acceleration and something causing movement.

The net effect of an object's gravitational attraction can be worked out by "adding up" (using something called integration) the contirbutions from each tiny bit of mass it's made up of, so if what i think you meant is correct it is the whole object "producing the field".

 

[flyingpig]

Electric fields may accelerate charged subatomic particles (such as electrons) as may gravitational fields, but neither need be present for the particle to be moving. Be careful to make sure you understand the difference between something causing acceleration and something causing movement.

Aha! Then what about inside a conductor? My book says that the E-field inside a conductor is 0 and if it was not 0 then they would experience a force F = qE. So that is why I asked if electrons really do need a E-field to move. My book makes it sound like the electrons are stuck or something.

 

[SammyS]

Do electrons need an electric field to cause them to move? (or whatever your question really is) NO! The Sun emits charged particles all the time, mostly through thermal processes. Many of them are electrons. Also, electrons have mass so a gravitational field can propel them.

Those facts have nothing to do with the fact that a free electron will move under the influence of an electric field. The fact that an electron moves under the influence of an electric field does not mean that it will only move under the influence of an electric field.

No doubt, the author of your textbook is well regarded as a physicist. He/She is not making this stuff up just to mislead you.