Physics

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 torque $\stackrel{?}{\tau }$ acts on a body about a given point is found to be equal to $\stackrel{?}{A}*\stackrel{?}{L}$ where $\stackrel{?}{A}$ is a constant nonzero vector and $\stackrel{?}{L}$ is the angular momentum of the body about that point. Choose the incorrect option: $(\stackrel{?}{A}\ne \pm \hat{L})$

A beam of unpolarized light of intensity I? is incident on a polaroid A. Then it is passed through another polaroid B. If the intensity of the emergent light is 18% of the original unpolarized light then find the angle (nearest integer in degree) between the principal plane of polaroid A and B.

In the given circuit find the current through the Zener diode in mA.

A particle of mass 3 kg moving with speed of 3 m/s is acted upon by an impulse. As a result, the particle starts moving in a direction 90° to the original direction with a speed of 4 m/s. Find the impulse acted upon on the particle in SI units.

An inductor of inductance 0.1H and a resistor of resistance 8Ω are connected in series to a battery of emf 1.5 V through a switch. Find the initial rate of growth of current when the switch is closed (in A/s).