17. Four wires of same material, the same cross-sectional area and the same length when connected in parallel give a resistance of 0.25 Q. If the same four wires are connected is series the effective resistance will be
(a) 1 Q
(b) 2 Q
(c) 3 Q
(d) 4 Q
Ans: d
18. A current of 16 amperes divides between two branches in parallel of resistances 8 ohms and 12 ohms
respectively. The current in each branch is
(a) 6.4 A, 6.9 A
(b) 6.4 A, 9.6 A
(c) 4.6 A, 6.9 A
(d) 4.6 A, 9.6 A
Ans: b
19. Current velocity through a copper conductor is
(a) the same as propagation velocity of electric energy
(b) independent of current strength
(c) of the order of a few ^.s/m
(d) nearly 3 x 108 m/s
Ans: c
20. Which of the following material has nearly zero temperature co-efficient of resistance?
(a) Manganin
(b) Porcelain
(c) Carbon
(d) Copper
Ans: a
21. You have to replace 1500 Q resistor in radio. You have no 1500 Q resistor but have several 1000 Q ones which you would connect
(a) two in parallel
(b) two in parallel and one in series
(c) three in parallel
(d) three in series
Ans: b
22. Two resistors are said to be connected in series when
(a) same current passes in turn through both
(b) both carry the same value of current
(c) total current equals the sum of branch currents
(d) sum of IR drops equals the applied e.m.f.
Ans: a