Key Topic 3: Materials

Question 1

3-3A1: What metal is usually employed as a sacrificial anode for corrosion control purposes?

A. Platinum bushing.
B. Lead bar.
C. Zinc bar.
D. Brass rod.

Answer 1

C. Zinc bar.

Question 2

3-3A2: What is the relative dielectric constant for air?

A. 1
B. 2
C. 4
D. 0

Answer 2

A. 1

Question 3

3-3A3: Which metal object may be least affected by galvanic corrosion when submerged in seawater?

A. Aluminum outdrive.
B. Bronze through-hull.
C. Exposed lea keel.
D. Stainless steel propeller shaft.

Answer 3

D. Stainless steel propeller shaft.

Question 4

3-3A4: Skin effect is the phenomenon where:

A. RF current flows in a thinner layer of the conductor, closer to the surface, as frequency increases.

B. RF current flows in a thinner layer of the conductor, closer to the surface, as frequency decreases.

C. Thermal effects on the surface of the conductor increase the impedance.

D. Thermal effects on the surface of the conductor decrease the impedance.

Answer 4

A. RF current flows in a thinner layer of the conductor, closer to the surface, as frequency increases.

Question 5

3-3A5: Corrosion resulting from electrical current flow between dissimilar metals is called:

A. Electrolysis.
B. Stray current corrosion.
C. Oxygen starvation corrosion.
D. Galvanic corrosion.

Answer 5

D. Galvanic corrosion.

Question 6

3-3A6: Which of these will be most useful for insulation at UHF frequencies?

A. Rubber.
B. Mica.
C. Wax impregnated paper.
D. Lead.

Answer 6

B. Mica.