Question & Answer

Define surface texture.

Define nominal surface.

What are some of the reasons why surfaces are important?

What is meant by the term graduated measuring device?

What is precision in measurement?

What is accuracy in measurement?

What is the difference between a bilateral tolerance and a unilateral tolerance?

What is a tolerance?

Aluminum wiring was used in many homes in the 1960s due to the high cost of copper at the time. Aluminum wire that was 12 gauge (a measure of cross-sectional area) was rated at 15 A of current. If copper wire of the same gauge were used to replace the aluminum wire, what current should the wire be capable of carrying if all factors except resistivity are considered equal? Assume that the resistance of the wire is the primary factor that determines the current it can carry and the crosssectional area and length are the same for the aluminum and copper wires

A 16 gage nickel wire (0.0508-in diameter) connects a solenoid to a control circuit that is 32.8 ft away. (a) What is the resistance of the wire? Use Table 4.3 as a reference. (b) If a current was passed through the wire, it would heat up. How does this affect the resistance?

What is the resistance R of a length of copper wire whose length = 10 m and whose diameter = 0.10 mm? Use Table 4.3 as a reference

With reference to Table 4.2, determine the quantity of heat required to increase the temperature of an aluminum block that is 10 cm x 10 cm x 10 cm from room temperature (21°C) to 300°C.

With reference to Table 4.1, determine the increase in length of a steel bar whose length = 10.0 in, if the bar is heated from room temperature of 70°F to 500°F.

Aluminum has a density of 2.70 g/cm³ at room temperature (20°C). Determine its density at 650°C, using data in Table 4.1 as a reference.

A bridge built with steel girders is 500 m in length and 12 m in width. Expansion joints are provided to compensate for the change in length in the support girders as the temperature fluctuates. Each expansion joint can compensate for a maximum of 40 mm of change in length. From historical records it is estimated that the minimum and maximum temperatures in the region will be -35°C and 38°C, respectively. What is the minimum number of expansion joints required?

The starting diameter of a shaft is 25.00 mm. This shaft is to be inserted into a hole in an expansion fit assembly operation. To be readily inserted, the shaft must be reduced in diameter by cooling. Determine the temperature to which the shaft must be reduced from room temperature (20°C) in order to reduce its diameter to 24.98 mm. Refer to Table 4.1.

There are 12 correct answers in the following multiple choice questions (some questions have multiple answers that are correct). To attain a perfect score on the quiz, all correct answers must be given. Each correct answer is worth 1 point. Each omitted answer or wrong answer reduces the score by 1 point, and each additional answer beyond the correct number of answers reduces the score by 1 point. Percentage score on the quiz is based on the total number of correct answers.

4.1 Which one of the following metals has the lowest density: (a) aluminum, (b) copper, (c) magnesium, or (d) tin?

4.2 The thermal expansion properties of polymers are generally (a) greater than, (b) less than, or (c) the same as those of metals?

4.3 In the heating of most metal alloys, melting begins at a certain temperature and concludes at a higher temperature. In these cases, which of the following temperatures marks the beginning of melting: (a) liquidus or (b) solidus?

4.4 Which one of the following materials has the highest specific heat: (a) aluminum, (b) concrete, (c) polyethylene, or (d) water?

4.5 Copper is generally considered easy to weld because of its high thermal conductivity: (a) true or (b) false?

4.6 The mass diffusion rate dm/dt across a boundary between two different metals is a function of which of the following variables (four best answers): (a) concentration gradient dc/dx, (b) contact area, (c) density, (d) melting point, (e) thermal expansion, (f) temperature, and (g) time?

4.7 Which of the following pure metals is the best conductor of electricity: (a) aluminum, (b) copper, (c) gold, or (d) silver?

4.8 A superconductor is characterized by which of the following (one best answer): (a) high conductivity, (b) resistivity properties between those of conductors and semiconductors, (c) very low resistivity, or (d) zero resistivity?

4.9 In an electrolytic cell, the anode is the electrode that is (a) positive or (b) negative

What is an electrolyte?

What is dielectric strength as a material property?

Why are metals better conductors of electricity than ceramics and polymers?

Define resistivity as a material property.

What are the important variables that affect mass diffusion?

Define thermal diffusivity.

What is thermal conductivity as a material property?

Define specific heat as a material property