1
JEE Main 2018 (Online) 15th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A solid ball of radius R has a charge density $$\rho $$
given by $$\rho $$ = $$\rho $$o (1 $$-$$ $${\raise0.5ex\hbox{$\scriptstyle r$} \kern-0.1em/\kern-0.15em \lower0.25ex\hbox{$\scriptstyle R$}}$$) for 0 $$ \le $$ r $$ \le $$ R. The electric field outside the ball is :
A
$${{{\rho _o}{R^3}} \over {{ \in _o}{r^2}}}$$
B
$${{{\rho _o}{R^3}} \over {12{ \in _o}{r^2}}}$$
C
$${{4{\rho _o}{R^3}} \over {3{ \in _o}{r^2}}}$$
D
$${{3{\rho _o}{R^3}} \over {4{ \in _o}{r^2}}}$$
2
JEE Main 2018 (Online) 15th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A parallel plate capacitor with area 200 cm2 and separation between the plates 1.5 cm, is connected across a battery of emf V. If the force of attraction between the plates is $$25 \times {10^{ - 6}}N,$$ the value of V is approximately : $$\left( {{ \in _o} = 8.85 \times {{10}^{ - 12}}{{{C^2}} \over {N.{m^2}}}} \right)$$
A
250 V
B
100 V
C
300 V
D
150 V
3
JEE Main 2018 (Online) 15th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A copper rod of cross-sectional area A carries a uniform current I through it. At temperature T, if the volume charge density of the rod is $$\rho $$, how long will the changes take to travel a distance d ?
A
$${{2\rho \,d\,A} \over {\rm I}}$$
B
$${{2\rho \,d\,A} \over {{\rm I}\,T}}$$
C
$${{\rho \,d\,A} \over {{\rm I}\,}}$$
D
$${{\rho \,d\,A} \over {{\rm I}\,T}}$$
4
JEE Main 2018 (Online) 15th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A man in a car at location Q on a straight highway is moving with speed $$\upsilon $$. He decides to reach a point P in a field at a distance d from the highway (point M) as shown in the figure. Speed of the car in the field is half to that on the highway. What should be the distance RM, so that the time taken to reach P is minimum ?

JEE Main 2018 (Online) 15th April Evening Slot Physics - Motion Question 144 English
A
d
B
$${d \over {\sqrt 2 }}$$
C
$${d \over 2}$$
D
$${d \over {\sqrt 3 }}$$
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