. Trade tests; the scientific measurement of trade proficiency . 218 TRADE TESTS. PICTURE 17 26. Q. What is shown at * A ?A. Fuse. 27. Q. What are the lamps at * B » used for? A. (i) Resistance. (2) Rheostat. (3) Regulate current. (One sufficient) 28. Q. What kind of current is suppUed at C ?A. Direct current (DC). PICTURE 18 29. Q. What is that?A. Rectifier. 30. Q. What kind of rectifier does that picture show?A. (i) Mercury. (2) Cooper-Hewitt. (One sufficient) 31. Q. What is a rectifier used for? A. To change alternating current (AC)to direct current (DC) or vice versa.

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