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8 months ago

Physics Physics Ray Optics and Optical Instruments

Given below are two statements : one is labeled as Assertion A and the other is labeled as Reason R.

Assertion A : For a simple microscope, the angular size of the object equals the angular size of the image.

Reason R : Magnification is achieved as the small object can be kept much closer to the eye that 25cm and hence it subtends a large angle.

In the light of the above statements, choose the most appropriate answer from the options given below:

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8 months ago

Physics Physics Electromagnetic Waves

A radiation is emitted by 1000W bulb and it generates an electric field and magnetic field at P, placed at a distance of 2m.Th efficiency of the bulb is 1.25%. The value of peak electric field at P is x * 10^-1 V/m. Value of x is----------. (Rounded – off to the nearest integer)

[Take $ε_{0} = 8.85 * 1 0^{- 12} C^{2} N^{- 1} m^{- 2}, c = 3 * 1 0^{8} m s^{- 1}]$

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Payal Gupta

Contributor-Level 10

$l = \frac{1}{2} c ε_{0} E_{0}^{2} = η * (\frac{P}{4 π r^{2}})$ Here $η$ is the efficiency

$E_{0} = \sqrt[]{\frac{η P}{2 π r^{2} c ε_{0}}} = \sqrt[]{\frac{1.25}{100} * \frac{1000}{2 * 3.14 * 4 * 3 * 1 0^{8} * 8.85 * 1 0^{- 12}}}$

$\Rightarrow E_{0} = \sqrt[]{\frac{12.5}{8 * 3.14 * 3 * 8.85 * 1 0^{- 4}}} = 13.69 V m = 136.9 * 1 0^{- 1} V / m$

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8 months ago

Physics Class 11th

A person standing on a balance inside a stationary lift measures 60 kg. The weight of that person if the lift descends with uniform downward acceleration of 1.8m/s² will be----------N. [g = 10 m/s²]

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Payal Gupta

Contributor-Level 10

mg – N = ma

N = m (g – a) = 60 * (10 – 1.8) = 60 * 8.2 = 492 N

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8 months ago

Physics Electromagnetic Induction

An aeroplane, with its wings spread 10m, is flying at a speed of 180 km/h in a horizontal direction. The total intensity of earth's field at that part is 2.5 * 10^-⁴Wb/m² and the angle of dip is 60°. The emf induced between the tips of the plane wings will be………….

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Vishal Baghel

Contributor-Level 10

Bv = B sin 60°

$B_{v} = 2.5 * 1 0^{- 4} * \frac{\sqrt[]{3}}{2}$

$E m f = B_{v} * v * l = 2.5 * 1 0^{- 4} * \frac{\sqrt[]{3}}{2} * 180 * \frac{5}{18} * 1 = 108.25 * 1 0^{- 3} v o l t s$

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8 months ago

Physics Thermodynamics

The internal energy (U), pressure (P) and volume (V) of an ideal gas are related as U = 3PV + 4. The gas is:

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Vishal Baghel

Contributor-Level 10

U = 3PV + 4

$\Rightarrow n C_{v} T = 3 P V + 4$

$\Rightarrow n * \frac{f R T}{2} = 3 P V + 4$

$\Rightarrow f = 6 + \frac{8}{P V}$

$\Rightarrow f > 6 \Rightarrow p o l y a t o m i c$

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8 months ago

Physics Physics Alternating Current

In a series LCR resonant circuit, the quality factor is measured as 100. If the inductance is increased by two fold and resistance is decreased by two fold, then the quality factor after this change will be--------.

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Payal Gupta

Contributor-Level 10

As we know that Q = $\frac{ω L}{R}$

$\Rightarrow \frac{Q'}{Q} = \frac{L'}{R'} * \frac{R}{L} = (\frac{L'}{L}) * (\frac{R}{R'}) = 2 * 2 \Rightarrow Q' = 4 Q = 4 * 100 = 400$

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8 months ago

Physics Physics Electrostatic Potential and Capacitance

If 'C' and 'V' represent capacity and voltage respectively then what are the dimensions of $λ$ where C/V = $λ$

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Vishal Baghel

Contributor-Level 10

$λ = \frac{c}{v} = \frac{Q^{3}}{W^{2}} = \frac{I^{3} T^{3}}{M^{2} L^{4} T^{- 4}} \Rightarrow [λ] = [M^{- 2} L^{- 4} T^{7} l^{3}]$

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8 months ago

Physics Physics Motion in Straight Line

A scooter accelerates from rest for time t₁ at constant rate a₁ and then retards at constant rate a₂ for time t₂ and comes to rest. The correct value of $\frac{t_{1}}{t_{2}}$ will be:

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Vishal Baghel

Contributor-Level 10

$t a n α = \frac{v_{m a x}}{t_{1}} = a_{1}$

$t a n β = \frac{v_{m a x}}{t_{2}} = a_{2}$

^{$\Rightarrow \frac{a_{1}}{a_{2}} = \frac{t_{2}}{t_{1}} \Rightarrow \frac{t_{1}}{t_{2}} = \frac{a_{2}}{a_{1}}$}

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8 months ago

Physics Class 11th

As shown in the figure, a block of mass $\sqrt[]{3} k g$ is kept on a horizontal rough surface of coefficient of friction $\frac{1}{3 \sqrt[]{3}} .$ The critical force to be applied on the vertical surface as shown at an angle 60° with horizontal such that it does not move, will be 3x. The value of x will be-------------.

[g = 10m/s² ; sin 60° = $\frac{\sqrt[]{3}}{2};$ cos60° = $\frac{1}{2}]$

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Payal Gupta

Contributor-Level 10

N = mg + F sin 60°

$f_{l i m} = F c o s 60 ° \Rightarrow μ N = F c o s 60 °$

$μ m g = F [c o s 60 ° - μ s i n 60 °]$

$F = \frac{μ m g}{c o s 60 ° - μ s i n 60 °} = \frac{\frac{1}{3 \sqrt[]{3}} * \sqrt[]{3} * 10}{\frac{1}{2} - \frac{1}{3 \sqrt[]{3}} * \frac{\sqrt[]{3}}{2}} = \frac{10 / 3}{\frac{1}{2} - \frac{1}{6}} = \frac{10 / 3}{1 / 3} = 10 N = 3 * (\frac{10}{3}) N$

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8 months ago

Physics Physics Oscillations

A particle executes S.H.M., the graph of velocity as a function of displacement is:

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Vishal Baghel

Contributor-Level 10

$v = ω \sqrt[]{A^{2} - x^{2}} \Rightarrow \frac{v^{2}}{A^{2} ω^{2}} + \frac{x^{2}}{A^{2}} = 1$ Path is ellipse.

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