Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice energy in wave motion oscillation and waves waves physics

A progressive wave on a string having linear mass density $\rho$ is represented by $y = A\sin \left (\dfrac {2\pi}{\lambda} x - \omega t\right )$ where $y$ is in $10\ mm$. Find the total kinetic energy (in $\mu l)$ passing through origin from $t = 0$ to $t = \dfrac {\pi}{2\omega}$.
[Take : $\rho = 3\times 10^{-2} kg/ m; A = 1mm; \omega = 100\ rad/ sec; \lambda = 16\ cm]$

  1. $6$

  2. $7$

  3. $8$

  4. $9$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The kinetic energy passing through a point is calculated by integrating the power or using the energy density formula. Given the parameters, the calculation leads to 9.

Multiple choice energy in wave motion oscillation and waves waves physics

A clamped string is oscillating in nth harmonic, then 

  1. total energy of oscillations will be $n^{2}$ times that of fundamental frequency

  2. total energy of oscillations will be $(n-1)^{2}$ times that of fundamental frequency

  3. average kinetic energy of the string over a complete oscillations is half of the total energy of the string

  4. none of these
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

For a sine wave, $y = A \sin(kx -  \Omega  t)$
Velocity equation for this wave is $V _y =  \Omega A \cos(kx - \Omega  t)$
Kinetic energy = $ d(KE) = 1/2(V _y^2 \times dm) = 1/2(V _y^2 \times  \mu  dx)$, $ \mu $ is the linear mass density.


=> $1/2( \mu  \times  \Omega ^2 \times A^2 \times cos^2(kx -  \Omega  t)) dx$
integrating at $t = 0,$ with limits as $0$ and $ \lambda $, we have

$K.E = 1/4( \mu \times \Omega^2 \times A^2 \times  \lambda $)
Potential energy, $dU = 1/2 (  \Omega  ^2 \times y^2 \times  \mu ) dx $

integrating at $t = 0$, with limits as $0$ and $ \lambda $, we have
$U = 1/4( \mu \times \Omega  ^2 \times A^2 \times  \lambda $)

Total energy $E = K.E + U
$
=> $E = 1/2( \mu  A^2  \lambda $)
Therefore, for the first and fundamental frequency, energy is 
$E _1 = (1/2( \mu  A^2  \lambda ))/n^2$
And clearly from the above derivation, we have, K.E is half the total energy.

Multiple choice energy in wave motion oscillation and waves waves physics

To determine the position of a point like object precisely ______ light should be used.

  1. polarized

  2. short wavelength

  3. long wavelength

  4. intense
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
To determine the position of a point like object precisely light of short wavelength should be used.

Multiple choice physics magnetic effects of electric current direct current types of current movement of charge

In the direct current:

  1. The direction of current is always positive

  2. The direction of current is always negtive

  3. The direction of current changes constantly

  4. The direction of current is always in the same direction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

D
Direct current is an electric current generated by the charge carriers (electrons) that are flowing in only one direction. So, the DC current flows only in one direction. DC current is produced be the sources such as batteries, thermocouple, fuel cells, solar cells.

Multiple choice physics magnetic effects of electric current direct current types of current movement of charge

What is the voltage of the electricity that is generally supplied to a house ?

  1. $400 V$

  2. $200 V$

  3. $220 V$

  4. $260 V$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Worldwide, many different mains power systems are found for the operation of household and light commercial electrical appliances and lighting. The different systems are primarily characterized by the following.

  • Voltage
  • Frequency
  • Plugs and sockets (receptacles or outlets)
  • Earthing system (grounding)
  • Protection against overcurrent damage (e.g., due to short circuit), electric shock, and fire hazards.
  • Parameter tolerances.
All these parameters vary among regions. The voltages are generally in the range 100 to 240 V. The two commonly used frequencies are 50 and 60 Hz. Single-phase or three-phase power is most commonly used today.
In India, a voltage of nearly 220 volts and a frequency of 50 cycles per second is used.
Hence correct option is option C

Multiple choice physics magnetic effects of electric current direct current types of current movement of charge

In a dry cell

  1. Chemical energy is converted into heat

  2. Electrical energy is converted into electrical energy

  3. Chemical energy is converted into electrical energy

  4. Chemical energy is constant
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A Dry cell is a type of electricity producing chemical cell, commonly used for many home and portable devices , often in the form of batteries. it was developed in 1886 by German scientist Carl Gassner. 

A dry cell  is designed to convert it's chemical energy into electrical energy.
hence option C is correct.