Question 1

Laser light has a single frequency with constant amplitude and _________.

Accepted Answer

B

Question 2

The ways in which a laser can be used for aligning systems are limited only by ____________.

Accepted Answer

The statement suggests that the use of laser for alignment is limited only by the creativity and inventiveness of the user, implying that there are no inherent restrictions or constraints. Therefore, the correct choice is C, the ingenuity of the users. The question implies that there are no inherent limitations to the ways in which a laser can be used for aligning systems other than the creativity and resourcefulness of the users. The power of motors and the laws of light may play a role in the specific applications of laser alignment, but they are not the primary determinants of what is possible with this technology. Light dispersion may be a relevant consideration, but it is not mentioned in the question as a limiting factor.

Question 3

Five quantities must be known if the machinery is to be set up with the correct pulley sizes.

Accepted Answer

False

Question 4

Offset drives, such as V-belts, gears, and chain drives, can be lined up more easily than direct drives.

Accepted Answer

Offset drives, such as V-belts, gears, and chain drives, can be lined up more easily than direct drives because they allow for some misalignment between the shafts.

Question 5

Most electrically driven constant-speed machines operate at speeds below _________rpm.

Accepted Answer

Most electrically driven constant-speed machines, such as induction motors, operate at speeds below 1800 rpm. This is because the frequency of the power supply in most countries is 50 or 60 Hz, which corresponds to a synchronous speed of 1500 or 1800 rpm for a four-pole motor. Higher speeds would require more poles or a different power supply frequency. Most electrically driven constant-speed machines, such as motors or generators, operate at speeds below 1800 rpm. This is because the frequency of the AC power supply in the United States is 60 Hz, which corresponds to a speed of 1800 rpm for machines with four poles. Machines with different numbers of poles will have different synchronous speeds, but they will still operate at speeds below 1800 rpm in most cases. Options B, C, and D are all above 1800 rpm and therefore not the best choice.

Question 6

Induction motors are rarely used for operation at speeds below_________ rpm.

Accepted Answer

Induction motors are designed to operate within a certain range of speeds, typically above 500 rpm. Operating below this speed can cause the motor to overheat and can also result in reduced efficiency and power output. Therefore, choice A (500 rpm) is the best option. Induction motors are designed to operate at synchronous speed which is determined by the frequency of the power supply and the number of poles in the motor. As the number of poles in the motor decreases, the synchronous speed increases. The most common speeds for induction motors are 1800 rpm (4 poles), 1200 rpm (6 poles), and 900 rpm (8 poles). Speeds below 900 rpm are possible with induction motors, but they require a high number of poles which can make them bulky and expensive. Therefore, induction motors are rarely used for operation at speeds below 500 rpm.

Question 7

A vertical drive can cause problems because _________tends to pull the belts away from the lower sheave.

Accepted Answer

Gravity pulls objects in a vertical direction, which can cause the belts to be pulled away from the lower sheave in a vertical drive. Gravity pulls down on the belts, causing them to angle away from the lower sheave and potentially slip off.

Question 8

It has been suggested that synchronous motors are more expensive to install than squirrel cage motors if the rating exceeds 1 hp.

Accepted Answer

The answer of It has been suggested that synchronous motors...

Question 9

Laser light is directional.

Accepted Answer

Laser light consists of coherent, monochromatic and directional light waves. Laser light is highly directional and focused, meaning it travels in a straight line and maintains its intensity over long distances.

Question 10

The most economical speed for an electrical motor is about 1800 revolutions per minute.

Accepted Answer

This statement is generally true for standard induction motors in North America, where the frequency of the electrical supply is 60 Hz. However, it may not apply to all types of electrical motors or in regions with different electrical frequencies. This is generally true for a standard induction motor operating on a frequency of 60 Hz in the United States. However, the most economical speed for a motor can vary depending on the application and specific motor design.

Quiz 52: Direct Drives and Pulley Drives