Class 12th

Contributor-Level 10

$\frac{1}{V_{1}} + \frac{1}{30} = \frac{1}{10}$

V₁ = 15 cm

$\frac{1}{V_{2}} - \frac{1}{10} = - \frac{1}{10}$

$\Rightarrow V_{2} = \infty$

$\Rightarrow V_{3} = 30 c m$

$\Rightarrow O V_{3} = 75 c m$

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11 months ago

For a transistor a and b are given as $α = \frac{I_{C}}{I_{E}} a n d β = \frac{I_{C}}{I_{B}} .$ Then the correct relation between a and b will be:

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Contributor-Level 10

β $= \frac{I_{C}}{I_{E}} = \frac{I_{C}}{I_{E} - I_{C}} = \frac{I_{C} / I_{E}}{1 - l_{C} / I_{E}} = \frac{α}{1 - α}$

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New answer posted

11 months ago

For full scale deflection of total 50 divisions, 50 mV voltage is required in galvanometer. The resistance of galvanometer if its current sensitivity is 2 div/mA will be:

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Class 12th Electromagnetic Waves

Contributor-Level 10

Current at full deflection,

$l_{m a x} = \frac{50}{2} = 25 m A$

$R = \frac{V}{l_{m a x}} = \frac{50}{25} = 2 K Ω$

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New answer posted

11 months ago

Electric field in a plane electromagnetic wave is given by

E = 50 sin(500x – 10 * 10¹⁰t) V/m

The velocity of electromagnetic wave in this medium is:

(Given C = speed of light in vacuum)

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Contributor-Level 10

$V = \frac{c o e f f i c i e n t o f t i m e}{c o e f f i c i e n t o f x} = \frac{ω}{k}$

$\Rightarrow V = \frac{10 * 1 0^{10}}{500} = 2 * 1 0^{8} = \frac{2 * c}{3}$

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New answer posted

11 months ago

For a transistor in CE mode to be used as an amplifier, it must be operated in:

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Contributor-Level 10

Active region of the CE transistor is linear region and is best suited for its use as an amplifier.

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11 months ago

A coaxial cable consists of an inner wire of radius 'a' surrounded by an outer shell of inner and outer radii 'b' and 'c' respectively. The inner wire carries an electric current i₀, which is distributed uniformly across cross-sectional area. The outer shell carries an equal current in opposite direction and distributed uniformly. What will be the ratio of the magnetic field at a distance x from the axis when (i) x < a and(ii) a < x < b?

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Contributor-Level 10

For x < a,

B₁ = $\frac{μ_{0} i_{0} x}{2 π a^{2}}$

For a < x < b,

$B_{2} = \frac{μ_{0} i_{0}}{2 π x}$

$\frac{B_{1}}{B_{2}} = \frac{x^{2}}{a^{2}}$

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New answer posted

11 months ago

The colour coding on a carbon resistor is shown in the given figure. The resistance value of the given resistor is:

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Contributor-Level 10

$R = 75 * 1 0^{2} \pm 5 %$

$\Rightarrow R = 7500 \pm 375 Ω$

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New answer posted

11 months ago

In Millikan's oil drop experiment, what is viscous force acting on an uncharged drop of radius 2.0 * 10^-⁵m and density 1.2 * 10³ kgm^-³? Take viscosity of liquid = 1.8 * 10^-⁵ Nsm^-². (Neglect buoyancy due to air).

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Contributor-Level 10

Viscous force = Weight

$\Rightarrow F_{V} = ρ * \frac{4}{3} π r^{3} * g = 3.9 * 10 N^{- 10}$

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New answer posted

11 months ago

An antenna is mounted on a 400m tall building. What will be the wavelength of signal that can be radiated effectively by the transmission tower upto a range of 44kg?

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Contributor-Level 10

Kindly go through the solution

$λ > h \Rightarrow λ > 400 m$

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New answer posted

11 months ago

Five identical cells each of internal resistance $1 Ω$ and emf 5V are connected in series and in parallel with an external resistance 'R'. For what value of 'R', current in series and parallel combination will remain the same?

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