1
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
When a semiconducting device is connected in series with a battery and a resistance, a current is found to flow in the circuit. If however, the polarity of the battery is reversed, practically no current flows in the circuit. The device may be
A
a p-type semiconductor
B
a n-type semiconductor
C
an intrinsic semiconductor
D
a p-n junction
2
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
The dimension of the universal constant of gravitation, G is
A
$$[M{L^2}{T^{ - 1}}]$$
B
$$[{M^{ - 1}}{L^3}{T^{ - 2}}]$$
C
$$[{M^{ - 1}}{L^2}{T^{ - 2}}]$$
D
$$[M{L^3}{T^{ - 2}}]$$
3
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Two particles A and B (both initially at rest) start moving towards each other under a mutual force of attraction. At the instant, when the speed of A is v and the speed of B is 2v, the speed of the centre of mass is
A
zero
B
v
C
$${{3v} \over 2}$$
D
$$-$$ $${{3v} \over 2}$$
4
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Three vectors $$\overrightarrow A $$ = a$$\widehat i$$ + $$\widehat j$$ + $$\widehat k$$; $$\overrightarrow B $$ = $$\widehat i$$ + b$$\widehat j$$ + $$\widehat k$$ and $$\overrightarrow C $$ = $$\widehat i$$ + $$\widehat j$$ + c$$\widehat k$$ are mutually perpendicular ($$\widehat i$$, $$\widehat j$$ and k are unit vectors along X, Y and Z-axes respectively). The respective values of a, b and c are
A
0, 0, 0
B
$$ - {1 \over 2}$$, $$ - {1 \over 2}$$, $$ - {1 \over 2}$$
C
1, $$-$$1, 1
D
$${1 \over 2}$$, $${1 \over 2}$$, $${1 \over 2}$$
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