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Multiple choice physics free, damped and forced oscillations melde's experiment free, forced and damped oscillations sonometer and laws of transverse vibrations

A string of length $36cm$ was in unison with a fork of frequency $256Hz$. It was in unison with another fork when the vibrating length was $48cm$, the tension being unaltered. The frequency of second fork is   

  1. $212Hz$

  2. $320Hz$

  3. $384Hz$

  4. $192Hz$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$f=\dfrac{v }{2L}$
$v =f(2\ L)$
$=256\times 2\times 36$
$=18432\ cm/s.$


wave velocty remains same
$f=\dfrac{v }{2L}$
$=\dfrac{18432}{2\times 48}$
$=192\ Hz.$

Multiple choice physics free, damped and forced oscillations melde's experiment free, forced and damped oscillations sonometer and laws of transverse vibrations

The total mass of a wire remains constant on stretching the length of wire to four times. It's frequency will become:

  1. 4 times

  2. 1/2 times

  3. 8 times

  4. $\sqrt{2}$ times
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Frequency, $f=\dfrac{1}{2l}\sqrt{\dfrac{t}{\mu }}$


Length is made four times, but mass is same.

$\Rightarrow$ Mass per unit length is $\mu'=\dfrac{\mu }{4}$

$\Rightarrow f'=\dfrac{1}{2(4l)}\sqrt{\dfrac{t}{\frac{\mu }{4}}}$$=\dfrac{2}{2(4l)}\sqrt{\dfrac{t}{\mu }}$ 

$\Rightarrow \dfrac{f'}{f}=\dfrac{1}{2}$

$\Rightarrow f'=\dfrac{f}{2}$

Multiple choice physics free, damped and forced oscillations melde's experiment free, forced and damped oscillations sonometer and laws of transverse vibrations

The length and diameter of a metal wire is doubled. The fundamental frequency of vibration will change from '$n$' to (Tension being kept constant and material of both the wires is same)

  1. $\dfrac { n }{ 4 } $

  2. $\dfrac { n }{ 8 } $

  3. $\dfrac { n }{ 12 } $

  4. $\dfrac { n }{ 16 } $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Fundamental frequency of vibration $n = \dfrac{v}{2L} \sqrt{\dfrac{T}{\mu}}$ 

where $\mu$ is the mass per unit length of the wire i.e. $\mu = \dfrac{M}{L}$
Mass of the wire $M = \rho (\dfrac{4\pi}{3} R^3)$
$\implies$ $n = \dfrac{v}{2L} .\sqrt{\dfrac{TL}{\rho \dfrac{4\pi }{3} R^3}}$
$\implies$ $n \propto \dfrac{1}{R\sqrt{LR}}$      .....(1)
Given :  $L _2 = 2L$  $R _2 = 2R$
From equation (1), we get  $\dfrac{n _2}{n} = \dfrac{R \sqrt{RL}}{R _2 \sqrt{L _2 R _2}}$
Or  $\dfrac{n _2}{n} = \dfrac{R \sqrt{R L}}{(2R) \sqrt{(2L) (2R)}}   = \dfrac{1}{4}$
$\implies$  $n _2 = \dfrac{n}{4}$

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

The slew rate of an opamp is found to be 10 V/microsecond. A voltage change of 100V will produce a time delay of

  1. 10 micro seconds

  2. 1 micro second

  3. 5 micro seconds

  4. 1 sec
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Slew rate describes the time delay the opamp offers to changes in input voltage. Thus a change of 100V will take 10 micro second in the output to describe.

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

In which of the following are operational amplifiers (op-amps) used?

  1. Oscillators

  2. Filters

  3. Instrumentation circuits

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

1.The oscillator circuits consists of a negative gain op-amp and a three section $RC$ network that produced the $180^{o}$phase shift.The phase shift network is connected from op-amp output back to its inverting input.

2. Op-amp  can be used in active filters as a active components.
3. Instrumentation amplifiers is a type of differential amplifiers that has been outfitted with input buffers amplifiers.so, op-amp are used in instrumentational circuits.
Therefore,op-amp can be used as a oscillators,filters and instrumentation circuits.

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

The output signal of an op-amp is _____ out of phase with its input signal connected to the inverting input terminal.

  1. 0

  2. 90

  3. 180

  4. 270
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

If the signal is through the inverting terminal, output will appear 180 degrees out of phase, while if the input is through the non-inverting terminal, output will be in phase with the input

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

Opamps are:

  1. made out of a single electronic component

  2. made out of a set of transistors, resistors and other components

  3. batteries used for amplifying signals

  4. circuits that can oscillate the input signal
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An operational amplifier (op-amp) is an integrated circuit consisting of many transistors, resistors, and capacitors designed to perform mathematical operations.

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

An input applied to either input terminal will result in _____.

  1. outputs from both output terminals, which have opposite polarities

  2. outputs from both output terminals, which have the same polarities

  3. a single output from one of the output terminals

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a differential amplifier configuration, an input applied to one terminal results in outputs at both terminals that are equal in magnitude but opposite in phase (polarity).