Class 12th

Two point charges $-\mathrm{q}$ and $+\mathrm{q}$ are placed at a distance of L, as shown in the figure.

The magnitude of electric field intensity at a distance $R(R>>L)$  varies as :

A big circular coil of 1000 turns, and average radius 10 m is rotating about its horizontal diameter at 2 rad ${\mathrm{s}}^{-1}$ . If the vertical component of earth's magnetic field at that place is $2*{10}^{-5}\mathrm{T}$ and electrical resistance of the coil is $12.56\mathrm{\Omega }$ , then the maximum induced current in the coil will be:

The area of rectangular field (in ${\mathrm{m}}^2$ ) of length $55.3\mathrm{m}$ and breadth 25 m after rounding off the value of correct significant digits is:

The graph which shows the vartiation of the de-Broglie wavelength $\left(\lambda \right)$  of a particle and its associated momentum (p) is :

A very long conducting wire is bent in a semi-circular shape from $\mathrm{A}$ to $\mathrm{B}$ as shown in figure. The magnetic field at point $\mathrm{P}$  for steady current configuration is given by:

10 resistors, each of resistance $\mathrm{R}$ are connected in series to a battery of emf $\mathrm{E}$ and negligible internal resistance. Then those are connected in parallel to the samebattery, the current is increased $\mathrm{n}$ times. The value of $n$  is:

The resistance of platinum wire at $0^{\circ }\mathrm{C}$ is $2\mathrm{\Omega }$ and $6.8\mathrm{\Omega }$ at ${80}^{\circ }\mathrm{C}$ . The temperature coefficient of resistance of the wire is:

An electric dipole is placed as shown in the figure

The electric potential (in $102\mathrm{V}$ ) at point $\mathrm{P}$ due to the dipole is $\left({?}_0=\right.$ permittivity of free space and $\left.\frac{1}{4\pi {?}_0}=K\right)$  :

A long solenoid of radius 1mm has 100 turns per mm. if 1 A current flows in the solenoid, the magnetic field strength at the centre of the solenoid is:

A biconvex lens has radii of curvature, 20cm each, If the refractive index of the material of the lens is 1.5 , the power of the lens is: