Tag: physics

Questions Related to 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 : $\rho = 3\times 10^{-2} kg/ m; A = 1mm; \omega = 100\ rad/ sec; \lambda = 16\ cm]$

energy in wave motion oscillation and waves waves physics

  1. $6$

  2. $7$

  3. $8$

  4. $9$

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Correct Option: D

A clamped string is oscillating in nth harmonic, then 

energy in wave motion oscillation and waves waves physics

  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

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Correct Option: A,C
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.

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

energy in wave motion oscillation and waves waves physics

  1. polarized

  2. short wavelength

  3. long wavelength

  4. intense

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Correct Option: B
Explanation:
To determine the position of a point like object precisely light of short wavelength should be used.

Dry cell is a source of

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

  1. Direct current

  2. Alternating current

  3. Can be used as direct current source or alternating current source

  4. Cant say

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Correct Option: A
Explanation:

Dry cells produces direct current .


Answer-(A)

In the direct current:

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

  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

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Correct Option: D
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.

The current in the armature of a motor is reversed every half cycle due to the action of on:

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

  1. armature

  2. field coil

  3. brush

  4. commutator

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Correct Option: A

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

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

  1. $400 V$

  2. $200 V$

  3. $220 V$

  4. $260 V$

Show answer
Correct Option: C
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

In a dry cell

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

  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

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Correct Option: C
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.

Secondary cells are also knows as

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

  1. Electrolyte

  2. Accumulators

  3. Dry cell

  4. All

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Correct Option: B
Explanation:

Secondary cells also provide current as a result of chemical reaction, but they can be recharged after use because in these cells, the chemical reaction is reversible.

Which of the following is a source of direct current.

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

  1. Cell

  2. Electromagnet

  3. Bulb

  4. Switch

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Correct Option: A
Explanation:

Source of direct current are the cells. In a cell, the chemical energy changes in to the electrical energy when it sends current in a circuit.