1
IIT-JEE 2012 Paper 1 Offline
MCQ (More than One Correct Answer)
+4
-1
A cubical region of side $$a$$ has its center at the origin. It encloses three fixed point charges, $$-q$$ at $$\left( {0, - a/4,0} \right), + 3q$$ at $$\left( {0,0,0} \right)$$ and $$-q$$ at $$\left( {0, + a/4,0} \right).$$ Choose the correct option(s)
A
The net electric flux crossing the plane $$x=+a/2$$ is equal to the net electric flux crossing the plane $$x=-a/2$$
B
The net electric flux crossing the plane $$y=+a/2$$ is more than the net electric flux crossing the plane $$y=-a/2.$$
C
The net electric flux crossing the entire region is $${q \over {{\varepsilon _0}}}$$
D
The net electric flux crossing the plane $$z = + a/2$$ is equal to the net electric flux crossing the plane $$x=+a/2.$$
2
IIT-JEE 2012 Paper 1 Offline
+3
-1

A small mass m is attached to a massless string whose other end is fixed at P as shown in the figure. The mass is undergoing circular motion in the xy-plane with centre at O and constant angular speed $$\omega$$. If the angular momentum of the system, calculated about O and P are denoted by $${\overrightarrow L _O}$$ and $${\overrightarrow L _P}$$, respectively, then

A
$${\overrightarrow L _O}$$ and $${\overrightarrow L _P}$$ do not vary with time.
B
$${\overrightarrow L _O}$$ varies with time while $${\overrightarrow L _P}$$ remains constant.
C
$${\overrightarrow L _O}$$ remains constant while $${\overrightarrow L _P}$$ varies with time.
D
$${\overrightarrow L _O}$$ and $${\overrightarrow L _P}$$ both vary with time.
3
IIT-JEE 2012 Paper 1 Offline
+3
-1

A biconvex lens is formed with two planoconvex lenses as shown in the figure. Refractive index n of the first lens is 1.5 and that of the second lens is 1.2. Both curved surface are of the same radius of curvature R = 14 cm. For this biconvex lens, for an object distance of 40 cm, the image distance will be

A
$$-$$280.0 cm
B
40.0 cm
C
21.5 cm
D
13.3 cm
4
IIT-JEE 2012 Paper 1 Offline
+3
-1

A thin uniform rod, pivoted at O, is rotating in the horizontal plane with constant angular speed $$\omega$$, as shown in the figure. At time t = 0, a small insect starts from O and moves with constant speed v, with respect to the rod towards the other end. It reaches the end of the rod at t = T and stops. The angular speed of the system remains $$\omega$$ throughout. The magnitude of the torque (|$$\tau$$|) about O, as a function of time is best represented by which plot ?

A
B
C
D
EXAM MAP
Medical
NEET