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Class 12th Chemistry

Leaching of gold with dilute aqueous solution of NaCN in presence of oxygen gives complex [A], which on reaction with zinc forms the elemental gold an another complex [B], [A] and [B], respectively are:

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Raj Pandey

Contributor-Level 9

Au + NaCN + O₂ ® Na [Au (CN)₂]

$Z n + N a [A u {(C N)}_{2}] \to N a_{2} [Z n {(C N)}_{4}] + A u$

$A i s {[A u {(C N)}_{2}]}^{-} a n d B i s {[Z n {(C N)}_{4}]}^{- 2}$

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Class 12th Physics Electromagnetic Waves

An electromagnetic wave of frequency 5 GHz, is travelling in a medium whose relative electric permittivity and relative magnetic permeability both are 2. Its velocity in the this medium is_____* 10⁷ m/s.

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alok kumar singh

Contributor-Level 10

$v = \frac{1}{\sqrt[]{ε μ}} = \frac{1}{\sqrt[]{2 ε_{0} . 2 μ_{0}}} = \frac{1}{2 \sqrt[]{ε_{0} μ_{0}}} = \frac{c}{2} = 15 * 1 0^{7} m / s .$

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Class 12th Physics

A common transistor ratio set requires 12V (D.C) for its operation. The D.C source is constructed by using a transformer and a rectifier circuit, which are operated at 220V (A.C) on standard domestic A.C, supply. The number of turns of secondary coil are 24, then the number of turns of primary are___________.

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alok kumar singh

Contributor-Level 10

$\frac{N_{p}}{N_{s}} = \frac{V_{p}}{V_{s}} \Rightarrow N_{p} = \frac{V_{p}}{V_{s}} * N_{s} = \frac{220}{12} * 24 = 440$

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2 months ago

Class 12th Physics Wave Optics

An unpolarized light beam is incident on the polarizes of a polarization experiment and the intensity of light beam emerging from the analyzer is measured as 100 Lumens. Now, if the analyzer is rotated around the horizontal axis (direction of light) by 30° in clockwise direction, the intensity of emerging light will be________ Lumens.

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alok kumar singh

Contributor-Level 10

$l = l_{0} c o s^{2} θ = 100 * c o s^{2} (30 °) = 75 L u m e n s$

Note : As the incident light is unpolarized, intensity of emerging light does not depend on the polarization axis of polarizer.

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Class 12th Physics

A resonance circuit having inductance and resistance 2 * 10^-4 H and 6.28 $Ω$ respectively oscillates at 10 MHz frequency. The value of quality factor of this resonator is__________.

[p = 3.14]

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alok kumar singh

Contributor-Level 10

Quality factor = $\frac{ω L}{R} = \frac{2 * 3.14 * 10 * 1 0^{6} * 2 * 1 0^{- 4}}{6.28} = 2000$

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Class 12th Physics

An audio signal V_m = 20 sin 2p(1500t) amplitude modulates a carrier

V_C = 80 sin 2p (100,000t)( The value of percent modulation is______________.

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alok kumar singh

Contributor-Level 10

Percentage Modulation = $\frac{A_{m}}{A_{c}} * 100 = \frac{20}{80} * 100 = 25 %$

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Class 12th Physics

In connection with the circuit drawn below, the value of current flowing through 2 $k Ω$ resistor is________ * 10^-4A.

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alok kumar singh

Contributor-Level 10

Potential difference across 2k $Ω$ is 5V, thus current through it,

$i = \frac{5}{2 * 1 0^{3}} = 25 * 1 0^{- 4} A .$

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Class 12th Physics Wave Optics

In a Young's double slit experiment, the width of the one of the slit is three times the other slit. The amplitude of the light coming from a slit is proportional to the slit-width. Find the ratio of the maximum to the minimum intensity in the interference pattern.

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alok kumar singh

Contributor-Level 10

Amplitude is proportional to the slit – width, thus,

$\frac{A_{1}}{A_{2}} = 3$

$\frac{l_{m a x}}{l_{m i n}} = \frac{{(A_{1} + A_{2})}^{2}}{{(A_{1} - A_{2})}^{2}} = \frac{{(\frac{A_{1}}{A_{2}} + 1)}^{2}}{{(\frac{A_{1}}{A_{2}} - 1)}^{2}} = \frac{{(3 + 1)}^{2}}{{(3 - 1)}^{2}} = 4 .$

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Class 12th Electromagnetic Induction

The current in a coil of self inductance 2.0 H is increasing according to I = 2sin(t2)A. The amount of energy spent during the period when current changes from 0 to 2 A is…………J.

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Raj Pandey

Contributor-Level 9

Given, L = 2H

l = 2 sin (t²)

$u = \int_{0}^{2} L i d i = \frac{L}{2} {[i^{2}]}_{0}^{2} = \frac{L}{2} [4 - 0]$

$u = \frac{2}{2} * 4 = 4 J$

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Class 12th Maths

Let g(x) = x + 2| - 3|. If a denotes the number of relative minima, b denotes the number of relative maxima and c denotes the product of the zeros. Then the value of (a + 2b - c) is __________

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Vishal Baghel

Contributor-Level 10

c = -5, a = 2, b = 1

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