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Multiple choice properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

 A certain inverting amplifier has a closed-loop voltage gain of 25. The Op-amp has an open-loop voltage gain of 100,000. If an Op-amp with an open-loop voltage gain of 200,000 is substituted in the arrangement, the closed-loop gain ..

  1. doubles

  2. drops to 12.5

  3. remains at 25

  4. increases slightly
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

the closed loop gain is given by $A _{cl}=\dfrac{A}{1+A \beta}$. since the open loop gain is large, the closed loop gain almost remains a constant, as it will be independent of open loop gain 

Multiple choice properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

Since the input impedance of an ideal operational amplifier is infinite.

  1. Its input current is zero

  2. Its output resistance is high

  3. Its output voltage becomes independent of load resistance

  4. It becomes a current controlled device
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Input current in an ideal operational amplifier   $i = \dfrac{V}{Z}$
Since,  input impedance of the ideal operational amplifier is infinite  $i.e. Z = \infty$
$\implies \ i =\dfrac{V}{\infty}= 0$

Multiple choice physics learning how to measure measuring length measurement of small and large distances measurement of distance unit of fundamental quantities

From the following, the biggest unit of energy is?

  1. Joule

  2. Kilowatt hour

  3. Erg

  4. Electron volt
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Since, we know that SI unit of energy is represented by Joule. Hence, let us convert all the different units in the form of Joules.


$1\,Joule=1\,Joule$

$1\,Kwh=3600000\,Joule$

$1\,erg=10^{-7}\,Joule$

$1\,eV=1.6\times 10^{-19}\,Joule$

Hence, Kilowatt hour is the largest unit of energy and hence it is practically used in everyday life of electric consumption.

Multiple choice physics motion and measurement measuring length measurement of small and large distances measurement of distance

Which one of the following methods is used to measure distance of a planet or a star from the earth?

  1. Echo method

  2. Parallax method

  3. Triangulation method

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Astronomers estimate the distance of nearby objects in space by using a method called stellar parallax, or trigonometric parallax. Simply put, they measure a star's apparent movement against the background of more distant stars as Earth revolves around the sun

Multiple choice physics motion and measurement measuring length measurement of small and large distances measurement of distance

'The parallax angle in radians is: $\theta = \left( 1 + \frac { 54 } { 60 } \right) \times \frac { \pi } { 180 } = 0.03316 \mathrm { rad }$
  Hence, the distance between moon and earth: 

  1. $\dfrac { \text { Diameter of Earth } } { \theta }$

  2. $\dfrac { 1.276 \times 10 ^ { 7 } m } { 0.03316 }$

  3. $3.84 \times 10 ^ { 8 } m$

  4. nnone of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given,

$\theta =0.03316\,\,rad$

Also $b = \mathrm { AB } =$ diameter of earth $= 1.276 \times 10 ^ { 7 } \mathrm { m }$

Now d $=\dfrac{b}{\theta }=\dfrac{1.276\times {{10}^{7}}}{0.03316\,}=3.84\times {{10}^{8}}\text{m}$

Hence, distance between earth and moon is $3.84\times {{10}^{8}}\text{m}$

Multiple choice physics motion and measurement measuring length measurement of small and large distances measurement of distance

Which of the following is the best method to measure microscopic distances?

  1. Optical microscope

  2. Meter scale

  3. Screw gauge

  4. Diffraction pattern
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Optical microscopes are enabled with objective fitted with lenses with different magnifications. This helps to magnify a small objects and so necessary measurements.

Multiple choice physics motion and measurement measuring length measurement of small and large distances measurement of distance

What is the approximation made in the parallax method?

  1. All distances measured between two points on earth is zero.

  2. All distances measured between two points on earth is constant.

  3. Distance between a point on the earth and the planet is very large as compared to the distance between two points on earth's surface.

  4. No approximation is made.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In parallax method, an approximation is made that distance between a point on the earth and the planet is very large as compared to the distance between two points on the earth's surface.

Multiple choice physics motion and measurement measuring length measurement of small and large distances measurement of distance

Two stars $S _1$ and $S _2$ are located at distances $d _1$ and $d _2$ respectively. Also if $d _1>d _2$ then which of the following statements is true?

  1. The parallax of $S _1$ and $S _2$ are same.

  2. The parallax of $S _1$ is twice as that of $S _2$.

  3. The parallax of $S _1$ is greater than parallax of $S _2$

  4. The parallax of $S _2$ is greater than parallax of $S _1$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$Answer:-$ D

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.Due to foreshortning, nearby objects have a larger parallax than more distant objects when observed from different positions, so parallax can be used to determine distances.

Hence parallax of $S _2$ is greater than that of $S _1$

Astronomersuse the principle of parallax to measure distances to the closer stars. Here, the term "parallax" is the semi-angle of inclination between two sight-lines to the star, as observed when the Earth is on opposite sides of the Sun in its orbit.