Monday, 7 January 2008 - 10:16 PM EST

1.When a conductor is placed within an electric field, the charges within the conductor will become polarized to prevent the electric field from penetrating the conductor.  Since the electric field does not penetrate the conductor, the area within the box is left undisturbed.

 2. One way that you can increase the capacitance of a capacitor is by decreasing the distance between the two plates.  This allows the two plates to attract the charges in the other plate more.  You can also increase the surface area of the plates which gives the charges more room to spread out from each other.  Finally you can add a dielectric between the two plates which allows for higher voltages before the charges will transfer between the plates.

Monday, 7 January 2008 - 10:23 PM EST

1. A conductor always has an internal electric field of 0 when the charges in it are not moving. When they are moving, the conductor has an electric field because F=qE. However, a conductor's electrons will move until the electric field is 0 again and the system is static. This can occur because the net charge distributes itself on the outside of the conductor. If there are two charges of the same sign, they will both repel eacch other towards the outside, because the field within the conductor must be 0. Because fields can and will exist outside of the conductor, the field in the conductor will be 0, passing the charges out of the conductor. This field will be perpendicular to the conductor's surface. This is because any parallel components of movement will be acted on by the system until they are in a position where they have no forces acting on them, at which point they will be perpendicular to the surface. An application of these characteristics of conductors is a car in a lightning storm. Because the leghtning will pass along th metal car (conductor),but a field cannot exist within it, so charges redistribute themselves on the outside of the car, leaving the passengers inside safe.

2. One way to increase capacitance is by decreasing the distancce between the capacitors plates. Because d is inversely proportional to C, a decrease in d will inccrease C.

A second way is to increase the size of the plates themselves. The formula for parallel plate capacitors shows that A is directly proportional to C so greater A leads to greater C.

A final way to increase C is by changing the dielectric. The dielectric is an insulator that keeps the plates from touching (d). The dielectric that would lead to the greatest charge would be one that is thin enough to have a very small d, but also one with a high dieleccric constant K, such as water.

Tuesday, 8 January 2008 - 8:09 AM EST

1. There are no electric fields within good conductors because the charges in the conductor itself polarizes in order to avoid the penetration of field charges. Electric fields are perpendicular to the conductor's surface because any parallel charges in the electric field will move along the surface until they reach spaces where no force is exerted on them - positions that are perpendicular to the surface. Some applications of the principle that electric fields don't penetrate capacitors are shield boxes for delecate instruments or electronic circuits that cannot have excess charges on them. Also, this principle explains why a car is one of the safest places to be during a lightning storm.

2. Three ways to increase the capacitance of a capacitor is to increase the area of the plates, move the plates closer together or adding a dielectric, since dielectrics allow the plates to be placed even closer together. To further increase the capacitance if a dielectric is already in place, you can change the dielectric to another material with a higher dielectric constant such as paper to mica.

Wednesday, 9 January 2008 - 9:22 PM EST

1.  An electric field inside any conductor is zero because, there are charges inside of a conductor and they polarize to avoid the filed charges from penetrating.  There would be a force on its free electrons.  So, the electrons would move until they reached positions where the electric field, and therefore the electric force on them, becomes zero.  The field outside is always perpendicular to the conductor's surface because if there were a component of E parallel to the surface, electrons at the surface would move along the surface in response to this force until they reached positions where no force was exerted on them, that is, until the electric field was perpendicular to the surface.  An application of these characteristics of conductors is when a car gets hit by a lightning.  The charge of lightning will pass through the metal part of the car, which is the conductor of electricity.  But, we know that there can be no field within the car so the charge of the lightning will end up redistributing itself on the outside, metal part of car, which leaves the driver and passengers safe within the vehicle.

2. One way that the capacitance of a capacitor can be increased is by placing the plates closer together without touching, which will allow an increased capacitance3because d is less.

Another way is to apply higher voltages without charge passing across the gap because of the insulating sheet called a dielectric between the plates.

A third way is that if the dielectric fills the space between the two conductors, the capacitance is increased by a factor K which is known as the dielectric constant.