Class 12th

An emf of  $20\mathrm{V}$ is applied at time $\mathrm{t}=0$ to a circuit containing in series $10\mathrm{m}\mathrm{H}$ inductor and $5\mathrm{\Omega }$ resistor. The ratio of the currents at time $t=\mathrm{\infty }$ and at $t=40\mathrm{s}$ is close to: (take $\left.{\mathrm{e}}^2=7.389\right)$

A sinusoidal voltage of peak value 250V is applied to a series LCR circuit, in which R = 8Ω, L = 24mH andC = 60μF. The value of power dissipated at resonant condition is ‘x’ kW. The value of x to the nearest integer is-----------.

In the logic circuit shown in the figure, if input A and B are 0 to 1 respectively, then output at Y would be ‘x’.

The value of x is ----------.

In the figure given, the electric current flowing through the 5 k Ω resistor is ‘x’ mA. The value of x to the nearest integer is --------.

The value of power dissipated across the Zener diode ( Vz = 15V) connected in the circuit as shown in the figure is x x10-1 watt. The value of x, to the nearest integer, is--------.

 

Two infinite planes each with uniform surface charge density +σ are kept in such a way that the angle between them is 30°. The electric field in the region shown between them is given by:

(A)
(B)
(C)
(D)

For an electromagnetic wave traveling in free space, the relation between average energy densities due to electric (Ue) and magnetic (Um) fields is :

The angle of deviation through a prism is minimum when

(A) Incident ray and emergent ray are symmetric to the prism

(B) The refracted ray inside the prism becomes parallel to its base

(C) Angle if incidence is equal to that of the angle of emergence

(D) When angle of emergence is double the angle of incidence

Choose the correct answer from the options given below :

In a parallel plate capacitor set up, plate area of capacitor is 2 m² and the plates are separated by 1m. If the space between the plates are filled with a dielectric material of thickness 0.5 m and area 2 m² (See fig) the capacitance of the set-up will be ______ ε₀. (Dielectric constant of the material = 3.2) (Round off to the Nearest Integer)

A 25 m long antenna is mounted on an antenna tower. The height of the antenna tower is 75m. The wavelength (in meter) of the signal transmitted by this antenna would be