Electric Charges
What are the two types of electric charge?
Positive and Negative
What does Coulomb’s Law calculate?
The electric force between two charges
What type of material allows charges to move freely?
Conductors
What is the direction of the electric field around a positive charge?
Away from the positive charge.
What is electric potential measured in?
Volts (V) or J/C
What is the unit of electric charge?
The coulomb (C)
How does the electric force change if the distance between two charges is doubled?
It becomes 1/4 as strong
Give one example of an insulator.
rubber, plastic, glass, wood, etc.
What is the unit of electric field?
Newtons per coulomb (N/C)
What is the relationship between electric field and electric potential?
The electric field is the negative slope of the electric potential (on a potential vs. position graph).
What particle carries a negative charge?
The electron
Write the formula for Coulomb’s Law.
F = kq1q2/r2
Give one example of a semiconductor.
Silicon, Germanium, GaN, GaAs, CdSe, etc.
What does the electric field represent physically?
The force per unit charge at a point
If the electric potential is constant over a region, what is the electric field there?
0 N/C
What is the fundamental electric charge (magnitude of charge of protons and electrons)?
Two charges of +1.0×10-6 C and +2.0×10-6 C are separated by 1.0 m. What is the force between them? Is it attractive or repulsive?
F=0.018 N (repulsive)
This term refers to charging an object through direct contact, allowing electrons to transfer.
Conduction.
A point charge of +2.0×10-6 C creates an electric field at a distance of 0.50 m. What is the magnitude of the electric field?
E = 7.19x104 N/C
What is the electric potential 0.30 m away from a point charge of +3.0×10-6 C?
9x104 V
If an object has a net positive charge, what does that mean about its electrons and protons?
It has more protons than electrons
Two identical charges repel each other with a force of 0.20 N when they are 0.30 m apart.
What is the magnitude of each charge?
This term refers to charging an object without contact, using a nearby charged object to rearrange charges.
Induction
Two charges lie on a line. One has a charge q1 = +4.0x10-6 C, and the other a charge of q2 = -2.0x10-6 C. They are 1.0 m apart. Find the net electric field at the midpoint between them.
E = 2.16x105 N/C
A proton (m=1.67×10-27 kg, q=+1.6×10-19 C) is released from rest at a point where the electric potential is 500 V. It moves to a point where the electric potential is 100 V. What is the speed of the proton at the 100 V point?
v = 2.8x105 m/s