VITEEE 2018 :: Physics :: General questions

• Physics - General questions

In a common emitter transistor amplifier β = 60, R₀ = 5000 Ω and internal resistance of a transistor is 500 Ω. The voltage amplification of amplifier will be

Answer:

Explanation:

Voltage amplification

$A_{v} = \beta\frac{R_{0}}{R_{i}}$ = $60\times\frac{5000}{500}$ = 600

Electron in hydrogen atom first jumps from third excited state to second excited state and then from second excited to the first excited state. The ratio of the wavelength λ₁: λ₂ emitted in the two cases is

Answer:

Explanation:

The wave number ($\bar{v}$) of the radiation = $\frac{1}{\lambda}$

= $R_{\infty}\left[\frac{1}{n_1^2}-\frac{1}{n_2^2}\right]$

Now for case (I) n₁= 3, n₂= 2

$\frac{1}{\lambda_{1}}=R_{\infty}\left[\frac{1}{9}-\frac{1}{4}\right]$

 R_∞ =  Rydberg constant

$\frac{1}{\lambda_{1}}=R_{\infty}\left[\frac{4-9}{36}\right]$

$=\left[\frac{-5R_{\infty}}{36}\right]$

$\lambda_{1}=\left[\frac{-36}{5R_{\infty}}\right]$

$\frac{1}{\lambda_{2}}=R_{\infty}\left[\frac{1}{4}-\frac{1}{1}\right]$

= $\left[\frac{-3R_{\infty}}{4}\right]$

$\lambda_{2}=\left[\frac{-4}{3R_{\infty}}\right]$

$\frac{\lambda_{1}}{\lambda_{2}}=\frac{-36}{5R_{\infty}}\times\frac{3R_{\infty}}{-4}$

$\frac{\lambda_{1}}{\lambda_{2}}$ = $\frac{27}{5}$

A metallic sphere is placed in a uniform electric field. The line of force follow the path (s) shown in the figure as

Answer:

Explanation:

The electric lines of force cannot enter the metallic sphere as the electric field inside the solid metallic sphere is zero. Also, the origination and termination of the electric lines of force from the metallic surface is normal (directed towards the centre).

The magnetic field at a point due to a current carrying conductor is directly proportional to

Answer:

Explanation:

The magnetic field produced due to a current-carrying conductor has the following characteristics:

• It encircles the conductor.
• It lies in a plane perpendicular to the conductor.
• The reversal in direction of current flow reverses the direction of the field.
• The strength of the field is directly proportional to the magnitude of the current.
• The strength of the field at any point is inversely proportional to the distance of the point from the wire.

So c is the answer

Which of the following is the correct lens formula?

Answer:

Explanation:

In optics, the relationship between the distance of an image (v), the distance of an object (u), and the focal length (f) of the lens is given by the formula known as Lens formula. ie

$\frac{1}{v}-\frac{1}{u}= \frac{1}{f}$

• Physics - General questions