Tag: physics

Questions Related to physics

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   

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

  1. $212Hz$

  2. $320Hz$

  3. $384Hz$

  4. $192Hz$

Show answer
Correct Option: D
Explanation:

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


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

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

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

  1. 4 times

  2. 1/2 times

  3. 8 times

  4. $\sqrt{2}$ times

Show answer
Correct Option: B
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 }}$ 

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

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

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)

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

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

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

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

  4. $\dfrac { n }{ 16 } $

Show answer
Correct Option: A
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  $\dfrac{n _2}{n} = \dfrac{R \sqrt{R L}}{(2R) \sqrt{(2L) (2R)}}   = \dfrac{1}{4}$
$\implies$  $n _2 = \dfrac{n}{4}$

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

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

  1. 10 micro seconds

  2. 1 micro second

  3. 5 micro seconds

  4. 1 sec

Show answer
Correct Option: A
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.

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

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

  1. Oscillators

  2. Filters

  3. Instrumentation circuits

  4. All of the above

Show answer
Correct Option: D
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.

The input resistance of op-amp is

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

  1. very high

  2. very low

  3. zero

  4. one

Show answer
Correct Option: A
Explanation:

For an ideal op-amp, the input impedance $R _i$ is infinite, so, we can say that the input resistance of op-amp is very high.

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

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

  1. 0

  2. 90

  3. 180

  4. 270

Show answer
Correct Option: C
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

Capacitors are not used as amplifiers because:

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

  1. They amplify signals of different frequencies by different amounts

  2. They only amplify AC signals

  3. They only amplify DC signals

  4. They introduce noise in addition to amplifying the signal

Show answer
Correct Option: A
Explanation:

Their voltage gain is non uniform for a range of frequencies

Opamps are:

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

  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

Show answer
Correct Option: B

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

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

  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

Show answer
Correct Option: A