# Naked Science Forum

## Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: cjohnson on 16/11/2009 14:58:35

Title: Physical forces and charges
Post by: cjohnson on 16/11/2009 14:58:35
I have two questions about physics forces.

First, I know that magetism and electricty are intimately linked (you can create one from the other).  My question is, how to magetic and electric fields interact.  For instance, if you electrostatically charge a ballon, will a magnet have an force on it?

Second, I don't know much about strong nuclear force, but weak nuclear for and electromagnetic force have charges +/- that attract/repell.  What about gravity?  All bodies attract each other through gravitational force.  Is there a real or theorized repulsive gravitational force?
Title: Physical forces and charges
Post by: Vern on 16/11/2009 18:07:33
Electromagnetic forces are described by partial differential equations. So a change in the amplitude of either creates the other. Maxwell wrote the equations that we still use to describe the electric and magnetic forces. But, Maxwell didn't know about the quantum nature of the fields his equations describe.

A charged balloon would tend to curve if moved through a magnetic field. Any charged particle tends to move in a curved path in a magnetic field. This tendency is useful for measurements in particle accelerators.
Title: Physical forces and charges
Post by: Mr. Scientist on 17/11/2009 10:46:58
They react because of motion. They are purely relativistic unified sides on on coin.
Title: Physical forces and charges
Post by: Soul Surfer on 17/11/2009 19:58:30
cjohnson  Your two questions (particularly the second) are very big and demand a whole physics text book to answer them and I reccommend that you start with some basic studies.

The answer to your electrically chaged ballon question is yes the electrically charged balloon and magnet will experience a force BUT ONLY WHEN THE BALLOON IS MOVING with respect to the magnet.  magnetism is produced by charges in motion.  Conversely electric fields are produced by magnets in motion.

There is no theoretical static repulsive gravitational force but in extreme conditions (kerr black holes where frame dragging occurs) repulsive forces due to gravitiational effects are possible between moving bodies.