Quiz

QUIZ

1. What are the units for the ampere in physics?

a. Coulombs per second b. Joules per second c. Charge per meter squared d. Volts per meter

Answer: a. The units for ampere involve the change in charge over the change in time, which are coulombs per second.

2. In any electrical situation, which charges flow and in which direction?

a. Only negative charges flow from negative to positive. b. Only positive charges flow from positive to negative. c. Both negative and positive charges flow from their highest energy level to the lowest energy level. d. Either positive or negative charges, or both can flow, depending on the electrical situation.

Answer: d. In metal electrical circuits, only negative charge flows. In ionic and biological systems both negative and positive charges flow, while the flow in van de Graaf generators, is of positive charges only.

3. When we think of flow of electrons, what is true of the density of electrons and their drift velocity?

a. The density will be directly proportional to the drift velocity. b. The density will be inversely proportional to the drift velocity. c. The density will be inversely proportional to the square root of the drift velocity. d. The density will be unrelated to the drift velocity.

Answer: b. The density of electrons will be inversely proportional to the drift velocity in that, the greater the density of electrons, the more the

electrons will bump into one another and will have a decreased drift velocity, which is the velocity of the electrons themselves.

4. According to Ohm’s law, what is true of what drives the current of an electric flow?

a. The potential difference or voltage applied b. The kinetic energy that is innate to electrons c. The electromagnetic repulsion of electrons d. The drift velocity of an electron in a conductor

Answer: a. The potential difference between two places or the voltage applied is what drives the current of electricity.

5. What system will have the greatest numbers of ohms associated with it?

a. Ceramic tube b. Copper wire c. Water d. Superconductor

Answer: a. Ceramic does not conduct electricity much at all so this would have the greatest resistance or the greatest number of ohms associated with it. Resistance is based on the shape of an object as well as on its substance.

6. What is referred to as the IR drop when a current travels through a resistor?

a. This is the loss of energy from the system as the electrons flow. b. This is the loss of voltage across a resistor. c. This is the kinetic energy increase across a resistor. d. This is the loss of thermal energy across a resistor.

Answer: b. The IR drop is the loss of voltage across a resistor. It is the change of kinetic energy of the circuit to thermal energy in the resistor.

7. What is the unit for power in electricity?

a. Joules b. Amperes per second c. Watts d. Watts per second

Answer: c. Watts are joules per second, which is the unit for power in electricity.

8. What are you paying for when it comes to your electric bill?

a. Current used b. Power used c. Voltage used d. Energy used

Answer: d. You are paying for the energy used, which is in kilowatthours. This equals to the number of joules used with the relationship being 1 kilowatt-hour equaling 3.6 x 106 Joules of energy.

9. What will the total resistance be when two resistors exist in series?

a. It will be equivalent to the resistance of the highest resistor and not related to the lowest resistor. b. It will be equivalent to the average resistance of the resistors in series. c. It will be resistances added together. d. It will be the resistances multiplied together.

Answer: c. The total resistance experienced when resistors are in series is equal to the sum of the resistances of the two resistors. The resistors will receive the same current but will split the voltages between them.

10. When resistors in an electrical system are in parallel, what is the total resistance of the system?

a. It will be the sum of the resistances together. b. It will be the resistances multiplied together. c. It will be the average of the resistances together. d. It will be less than the resistance of the smallest resistor.

Answer: d. The inverse of the total will be the additions of the inverses of the individual resistances. What this means is that the total resistance will be less than the resistance of the smallest resistor.