(A) dicalcium silicate (X)
(B) tricalcium silicate (X)
(C) tricalcium aluminate ()
(D) tetra calcium alumino ferrite (X)

Answers: The constituent of cement which is responsible for all the undesirable properties of cement is tricalcium aluminate.

(A) 10 minutes (X)
(B) 30 minutes ()
(C) 60 minutes (X)
(D) 600 minutes (X)

Answers: The initial setting time for ordinary Portland cement as per IS specifications should not be less than 30 minutes.

(A) Two SCR’s connected in reverse parallel ()
(B) Two SCR’s connected in parallel (X)
(C) Two SCR’s connected in series (X)
(D) Two BJT’s connected in series (X)

Answers: TRIAC is a semiconductor power electronic device which contains Two SCR’s connected in reverse parallel.

(A) both as forward characteristics (X)
(B) both as reverse characteristics (X)
(C) former as forward characteristics and later as reverse characteristics ()
(D) former as reverse characteristics and later as forward characteristics (X)

Answers: The curve between V and I of SCR when anode is positive w.r.t cathode and when anode is negative w.r.t cathode are known as  former as forward characteristics and later as reverse characteristics.

(A) as static conductor (X)
(B) for power control (X)
(C) for speed control of dc shunt motor (X)
(D) All of these ()

Answers: An SCR can be used All of these.

(A) breakdown voltage (X)
(B) peak reverse voltage (X)
(C) holding current ()
(D) latching current (X)

Answers: With gate open, the maximum anode current at which SCR is turned off from ON condition is called holding current.