An inner surface with charge would lead to a field inside. That cannot happen – inner surfaces are always regions of constant potential, and there is nowhere the electric field lines could end . The direction of conventional current is taken as the direction in which positive charge moves.

The repulsion between like charges makes it difficult to increase the number of charges in a volume. Thus, as one charge enters, another leaves almost immediately, carrying the signal rapidly forward. Find a straw and little peas that can move freely in the straw. Place the straw flat on a table and fill the straw with peas. When you pop one pea in at one end, a different pea should pop out the other end.

The net potential at P is that of the total charge placed at the common distance, . Note that this was simpler than the equivalent problem for electric field, due to the use of scalar quantities. Recall that we expect the zero level of the potential to be at infinity, when we have a finite charge. Note that we could have done this problem equivalently in cylindrical coordinates; the only effect would be to substitute r for x and z for y. Where is linear charge density, is the charge per unit area, and is the charge per unit volume. Give a plausible argument as to why the electric field outside an infinite charged sheet is constant.

Two charges of equal magnitude but opposite sign make up an electric dipole. A quadrupole consists of two electric dipoles are placed anti-parallel at two edges of a square as shown.Draw the electric field of the charge distribution. Compare the electric fields of an infinite sheet of charge, an infinite, charged conducting plate, and infinite, oppositely charged parallel plates. Where I is the current through a wire of cross-sectional area A made of a material with a free charge density n. The carriers of the current each have charge q and move with a drift velocity of magnitude vd. Describe the electric fields of an infinite charged plate and of two infinite, charged parallel plates in terms of the electric field of an infinite sheet of charge.

The reason for this problem may be traced to the fact that the charges are not localized in some space but continue to infinity in the direction of the wire. Hence, our assumption that zero potential must be an infinite distance from the wire is no longer valid. A general diagram of an electric dipole, and the notation for the distances from the individual charges to a point P in space. Recall that the electric field inside a conductor is zero. The voltage of this demonstration Van de Graaff generator is measured between the charged sphere and ground.

What is the best explanation for the observation that the electric charge on the stem became positive as the charged bee approached ? Because air is a good conductor, the positive charge on the bee’s surface flowed through the air from bee to plant. Because the earth is a reservoir of large amounts of charge, positive goofy skateboard games ions were drawn up the stem from the ground toward the charged bee. The plant became electrically polarized as the charged bee approached. Bees that had visited the plant earlier deposited a positive charge on the stem. Review The electric field 4.90 cm from a very long charged wire is (2200 N/C, toward the wire).

We can use these two quantities along with Avogadro’s number, 6.02 × 1023 atoms/mol, to determine n, the number of free electrons per cubic meter. A closed path for current to flow through is supplied by conducting wires connecting a load to the terminals of a battery. In this schematic, the battery is represented by the two parallel red lines, conducting wires are shown as straight lines, and the zigzag represents the load. The schematic represents a wide variety of similar circuits. Find the ratio of the diameter of aluminum to copper wire, if they have the same resistance per unit length .

The electron paths thus appear nearly random, like the motion of atoms in a gas. But there is an electric field in the conductor that causes the electrons to drift in the direction shown . The drift velocity vd is the average velocity of the free charges.