Sample Paper

589473
[Q. Booklet Number]

KOLKATA

B-JEE W B-JEE - 2 0 0 9
physical science & CHEMISTRY QUESTIONS & ANSWERS
1. One Kg of copper is drawn into a fit of 1mm diameter and a outfit of 2 mm diameter. The underground of the two wires will be in the dimension (A) 2 : 1 (B) 1 : 2 (C) 16 : 1 (D) 4 : 1 autonomic nervous system : (C) Hints : Mass =
2 1

(? r l )? (Ist wire) Mass = (? r l )? (2nd wire) (? r l )? = (? r l )?
2 1 1
2

2 1 1

2 2

2

l 1 ? r2 ? =? ? l 2 ? r1 ? ? ?

2

l1 2 R1 A1 l 1 A2 l 1 ? r2 ? = = × = ×? ? R2 ? l 2 l 2 A1 l 2 ? r1 ? ? ? A2

?

?r ? =? 2 ? ?r ? ? 1?

4

? 16 : 1
2. An electrical cable having a resistance of 0.2 ? delivers 10kw at 200V D.C. to a factory. What is the efficiency of transmission? (A) 65% (B) 75% (C) 85% (D) 95% Ans : (D) Hints : P = VI ? I =

10 × 103 = 50 A , Power mischief = (50)2 (0.2) = 500W 200

Efficiency =

10000 ×100 = 95.23% 10000 + 500

KOLKATA

3.

A wire of resistance 5 ? is drawn out so that its parvenu length is 3 times its original length.What is the reistance of the new wire? (A) 45 ? (B) 15 ? (C) 5/3 ? (D) 5 ? Ans : (A)

? r1 ? ? l 2 ? 3l Hints : ? ? = ? ?r ? ?l ?= l =3 ? ? 2? ? 1? ?r ? ? R2 ? l 2 A1 ? ?= × ? = 3 × ? 1 ? = 3 × 3 ? R2 = 45 ?R ?r ? ? 1 ? l 1 A2 ? 2?
4.



Two resembling cells each of emf E and internal resistance r are connected in parallel with an external resistance R. To get maximum world-beater developed across R, the take to be of R is (A) R = r/2 (B) R = r (C) R = r/3 (D) R = 2r Ans : (A) Hints : Req =
2

2

r r + 2R +R= 2 2

I=

2E r + 2R

For max. power consumption. I should be max. So denominator should be min. for that

r + 2R =
5.

(

r ? 2 R + 2 r 2R ? r ? 2R = 0 ? R = r / 2
(D) 4

)

2

To write the decimal number 37 in binary, how many binary digits are required? (A) 5 (B) 6 (C) 7 Ans : (B) Hints :

2 37 1 2 18 0 2 2 2 9 4 2 1
6. A junction semiconductor diode has a resistance of 25 ? when forward biased and 2500 ? when move up biased. The current in the diode, for the arrangement...If you want to get a abounding essay, order it on our website: Orderessay



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