Please read all questions carefully. Show all work when necessary for full credit.
Section I: True/False. Choose the correct answer.
1. A magnet moving near a coil of wire will induce a current in the wire.
a. True
b. False
2. A 9-volt battery is an example of an AC energy source.
a. True
b. False
3. In an AC-circuit, electrons carry the electric field through the wire.
a. True
b. False
4. The magnetic force on a moving charged particle can change the particle's direction.
a. True
b. False
Section II: Choose the answer that best completes the sentence.
1. If the magnitude of an electric field is tripled, the force felt by a nearby charge q will be _______________.
a. doubled
b. tripled
c. one third
d. one half
2. For a charge q moving through a magnetic field B, the magnetic force is always ________________ to the direction of the moving charge.
a. 45 degrees
b. 0 degrees
c. 90 degrees
d. 30 degrees
3. Faraday's Law states that the induced voltage in a coil of wire is proportional to _______________.
a. the length of the wire and the rate of change of the current
b. the rate of change of the voltage
c. the area of the magnetic field
d. the number of turns in the coil and the rate of change of the magnetic field
4. When Jenny combs her hair with a plastic comb, some of the electrons from her hair are transferred to the comb's surface. If she brings the comb near a small piece of paper, the atoms in the paper will be ________________ temporarily
a. electrically neutralized
b. insulated
c. electrically polarized
5. Two identical resistors in a circuit are connected in parallel. If a third identical resistor is added in parallel, the total resistance of the circuit will ________________.
a. decrease
b. stay the same
c. increase
d. increase then decrease
Section III: Solve. Show your work.
1. Two identical charged particles are 0.001 m apart. If they are moved to 0.003 m apart, by how much has the electrical force decreased?
2. What is the force between two electrons that are 1 µm apart? Note: 1 µm=10-6 m. The charge of an electron is 1.6 x 10-19 C.
3. What is the electric potential of a 0.25 µC charge with a potential energy of 40 J? Note: 1 µC=10-6 C.
4. A transformer is designed with a primary voltage of 100 V and a primary current of 20 A. If the secondary voltage is 120 V, what is the output current? Is this a step-up or step-down transformer?
5. What is the total resistance of a parallel circuits with resistors 10 ?, 20 ?, and 40 ?? If 100 V is applied to the circuit, what is the total current running through each resistor?