Physics NCERT Exemplar Solutions Class 11th Chapter Fifteen

A circular loop of radius R = 20 cm is placed in a uniform magnetic field B = 7 T in x-y plane as shown in figure. The loop carries a current $i=1.0\mathrm{A}$ in the direction shown in figure. The magnitude of torque acting on the loop is__ N.m. Take $\left.\pi =\frac{22}{7}\right\}$

 

A circular loop of radius R= 20cm is placed in a uniform magnetic field b= 7 T in x-y plane as shown in figure. The loop carries a current $i=1.0\mathrm{A}$ in the direction shown in figure. The magnitude of torque acting on the loop is__ N.m. Take $\left.\pi =\frac{22}{7}\right\}$

Three points masses $m,2m$ and 3m are located at the vertices of an equilateral triangle of side ' a '. The moment of inertia of the system about an axis along the altitude of the triangle passing through m is $\frac{N}{20}m{a}^2$ where N is an integer. The value of N is

Block of mass M slides down on frictionless incline as shown. The minimum friction coefficient so that block of mass m does not slide with respect to lower block is close to $\frac{I}{1000}$ , the nearest integer to I is $?\left(\mathrm{s}\mathrm{i}\mathrm{n}?{37}^{?}\approx \frac{3}{5}\right)\left\{\right.$ Take $\left.g=10\mathrm{m}/{\mathrm{s}}^2\right\}$

A $100\mathrm{e}\mathrm{V}$ electron collides with a stationary helium ion ${\mathrm{H}\mathrm{e}}^{+}$ in its ground state and excites it into higher energy level $n$ . After collision ${\mathrm{H}\mathrm{e}}^{+}$ ions emits two photons in succession with a wavelength $1085\text{?}$ and $304\text{?}$  to reach its ground state. Quantum number of excited state $n$  is

A double convex lens is made of glass which has its refractive index of 1.55 for violet rays and 1.50 for red rays. If the focal length for violet rays is 20cm, then the focal length for red rays will be cm.

The sum of two forces  $\vec{P}$ and $\vec{Q}$ is $\vec{R}$ such that $\left|\vec{R}\right|=\left|\vec{P}\right|$ . The angle $\theta$ (in degrees) that the resultant of $2\vec{P}$ and $\vec{Q}$ will make with $\vec{Q}$ is,               

The balancing length for a cell is $560\mathrm{c}\mathrm{m}$ in a potentiometer experiment. When an external resistance of $10\mathrm{\Omega }$ is connected in parallel to the cell, the balancing length changes by $60\mathrm{c}\mathrm{m}$ . If the internal resistance of the cell is $\frac{N}{10}\mathrm{\Omega }$ , where $N$ is an integer then value of $N$  is

A $60\mathrm{p}\mathrm{F}$ capacitor is fully charged by a $20\mathrm{V}$ supply. It is then disconnected from the supply and is connected to another uncharged $60\mathrm{p}\mathrm{F}$ capacitor in parallel. The electrostatic energy that is lost in this process by the time the charge is redistributed between them is (in $\mathrm{n}\mathrm{J}$  )

$\mathrm{M}$ grams of steam at ${100}^{\circ }\mathrm{C}$ is mixed with $200\mathrm{g}$ of ice at its melting point in a thermally insulated container. If it produces liquid water at ${40}^{\circ }\mathrm{C}$ [heat of vaporization of water is $540\mathrm{c}\mathrm{a}\mathrm{l}/\mathrm{g}$ and heat of fusion of ice is $80\mathrm{c}\mathrm{a}\mathrm{l}/\mathrm{g}$ ], the value of $M$  is