The composition of an insulating material is such that its solid constituents trap air (or gas) in extremely small volumes. Why does the entrapment of large volumes of air (or gas) reduce the insulating property of the material?
What will be an ideal response?
When large volumes of air (or gas) are trapped, convection currents are set up within the volumes of air, causing convection heat flow to occur. Because the purpose of an insulating material is to stop heat flow, large volumes of air (or gas) reduce the insulating property of the material.
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Which tool(s) are used to determine if a crankshaft straight?
A. V-blocks and dial indicator B. V-blocks and dial caliper C. Straight edge and feeler gauges D. Torque plate and straight edge
Which of the following is not permitted for the bonding required by 250.97?
A. Threadless couplings and connectors for cables with metal sheaths B. Two locknuts, on rigid metal conduit or intermediate metal conduit, one inside and one outside of boxes and cabinets C. Fittings with shoulders that seat firmly against the box or cabinet, with one locknut on the inside of boxes and cabinets D. One locknut outside the enclosure and one metal bushing inside the enclosure for rigid metal conduit or intermediate metal conduit
How much heat is required to increase the temperature of 20 lbs of water from 32°F to 212°F?
A) 212°F - 32°F = 180 BTUs B) 20 lbs × 180°F = 3,600 BTUs C) 20 lbs × 0.5 × 180°F = 1,800 BTUs D) (20 × 144 ) + (20 × 180 ) + (20 × 970 )=25,880 BTUs
Centerlines are used in exploded views to show the connection between part and subassembly axis.
Answer the following statement true (T) or false (F)