PHYSICS 7D Lecture Notes - Lecture 11: Valence And Conduction Bands, Charge Carrier, Electric Current

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PHYSICS 7D Lecture Notes - Lecture 10: Farad, Electric Field, Electrical Network

PHYSICS 7D Lecture Notes - Lecture 11: Valence And Conduction Bands, Charge Carrier, Electric Current

PHYSICS 7D Lecture Notes - Lecture 12: Ampere, Joule, Voltmeter

Document Summary

A conductor is a material in which some of the atomic electrons are not bound to individual atoms, they are free to wander around in the conductor. The net charge in the conductor is zero. There is typically one free electron (conduction electron) per atom. The conduction electrons are in random thermal motion, no net average motion. On average, the number of electrons crossing any plane in the conductor is zero: no net current. With an electric potential applied across a conductor: There is an electric field in the conductor-not in static equilibrium. The electric field in the conductor causes electrons to move opposite the direction of the e field-this is an electric current. Conventionally, positive current is the direction that positive charge carrier would move (opposite to the direction of the electron) A current can be produced by positive or negative charge flow. Conventional current is treated as a flow of positive charges.

Related Questions

Consider an electric dipole whose dipole moment (a vector pointing from the negative charge to the positive charge) is oriented at an angle with respect to the y-axis. There is an external electric field of magnitude E (independent of the field produced by the dipole) pointing in the positive y-direction. The positive and negative ends of the dipole have charges +q and -q, respectively, and the two charges are a distance d apart. The dipole has a moment of inertia I about its center of mass. It will help you to imagine that the dipole is free to rotate about a pivot through its center.

A) What is the net force that the dipole experiences due to the electric field?

B) What is , the magnitude of the torque that the electric field exerts about the center of mass of the dipole?

C) Using the above result, find the potential energy associated with the dipole's orientation in the field as a function of the angle shown in the figure. Take the zero of the potential to occur when the dipole is at angle ; that is , .

D) In terms of the dipole moment , What is the expression for the torque on a dipole in the field ?

E) In terms of the dipole moment, What is the expression for the potential energy of a dipole in the field?

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Two parallel plates (as in procedure 2) are parallel to the floor,distance 1.24 cm. The difference in potential between the plates is146 V, with the upper plate at the higher potential. Assume theplates are very large (so the electric field is approximatelystraight lines), and no other charges are nearby.

1) The direction of the field is:
a. upward above the plates, downward below the plates, upwardbetween the plates
b. downward above the plates, upward below the plates, downwardbetween the plates
c. upward above the plates, downward below the plates, downwardbetween the plates
d. downward above the plates, upward below the plates, zero betweenthe plates
e. zero outside of the plates, upward between the plates
f. downward above and below the plates, zero between theplates
g. upward above and below the plates, zero between the plates
h. downward above the plates, downward below the plates, downwardbetween the plates
i. downward above the plates, upward below the plates, upwardbetween the plates
j. zero outside of the plates, downward between the plates
k. upward above and below the plates, downward between theplates
l. upward above the plates, downward below the plates, zero betweenthe plates
m. downward above and below the plates, upward between theplates
n. upward above and below the plates, upward between theplates

2) As you move upward, from the negative plate to the positiveplate, the electric field will
a. have the same magnitude and remain in the same direction
b.increase in magnitude, remain in the same direction
c.decrease in magnitude, remain the the same direction
d.decrease in magnitude, reverse direction
e.have the same magnitude, reverse direction
f.increase in magnitude, reverse direction

c) An electron (mass 9.11x10-31 kg, charge 1.60x10-19 C) is placednear the negative plate. The force felt by the electron at thispoint is
_____ N

d) Suppose the electron starts at rest on the negative plate. Whenit arrives at the positive plate, its speed will be
_______ m/s

Two parallel plates (as in procedure 2) are parallel to the floor,distance 3.59 cm. The difference in potential between the plates is162 V, with the upper plate at the higher potential. Assume theplates are very large (so the electric field is approximatelystraight lines), and no other charges are nearby.

a) The direction of the field is (pick one)
1. downward above the plates, downward below the plates, downwardbetween the plates
2. zero outside of the plates, downward between the plates
3. zero outside of the plates, upward between the plates
4. upward above and below the plates, upward between theplates
5. upward above the plates, downward below the plates, upwardbetween the plates
6. downward above the plates, upward below the plates, upwardbetween the plates
7. downward above and below the plates, upward between theplates
8. downward above the plates, upward below the plates, zero betweenthe plates
9. upward above and below the plates, downward between theplates
10. downward above the plates, upward below the plates, downwardbetween the plates
11. upward above the plates, downward below the plates, downwardbetween the plates
12. downward above and below the plates, zero between theplates
13. upward above and below the plates, zero between theplates
14. upward above the plates, downward below the plates, zerobetween the plates

b) As you move upward, from the negative plate to the positiveplate, the electric field will (pick one)
1. increase in magnitude, remain in the same direction
2. decrease in magnitude, remain the the same direction
3. increase in magnitude, reverse direction
4. have the same magnitude, reverse direction
5. decrease in magnitude, reverse direction
6. have the same magnitude and remain in the same direction

c) An electron (mass 9.11x10-31 kg, charge 1.60x10-19 C) is placednear the negative plate. The force felt by the electron at thispoint is
_____ N

d) Suppose the electron starts at rest on the negative plate. Whenit arrives at the positive plate, its speed will be
________ m/s

PHYSICS 7D Lecture Notes - Lecture 11: Valence And Conduction Bands, Charge Carrier, Electric Current

PHYSICS 7D Lecture Notes - Lecture 10: Farad, Electric Field, Electrical Network

PHYSICS 7D Lecture Notes - Lecture 11: Valence And Conduction Bands, Charge Carrier, Electric Current

PHYSICS 7D Lecture Notes - Lecture 12: Ampere, Joule, Voltmeter

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