Tag: physics

Questions Related to physics

The magnetic moment of a short bar magnet placed with its magnetic axis at $30^0$ to an external field of $900$G and experiences a torque of $0.02$N m is going to be

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. $0.35 A m^2$

  2. $0.44 A m^2$

  3. $2.45 A m^2$

  4. $1.5 A m^2$

Show answer
Correct Option: B
Explanation:

Here, $B = 900 Gauss = 900 \times 10^{-4}T. = 9 \times 10^{-2}T$
$T = 0.02 N m and \theta = 30^0$
$\therefore T = mB sin \theta$
$\Rightarrow 0.02 = m \times 9 \times 10^{-2} \times sin 30^0$
$m = \dfrac{0.02 \times 2 }{9 \times 10^{-2}}= 0.44 A m^2$.

If a solenoid is having magnetic moment of $0.65 JT^{-1}$ is free to turn about the vertical direction and has a uniform horizontal magnetic field of $0.25$T applied. What is the magnitude of the torque on the solenoid when its axis makes an angle of $30^0$ with the direction of applied field is?

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. $0.075$N m

  2. $0.080$ N m

  3. $0.081$ N m

  4. $0.091$ N m

Show answer
Correct Option: C
Explanation:
Given that, $M=0.65 JT^{-1}$ , $B=0.25\ T$ and $\theta= 30^o$

$\therefore$ Torque on the solenoid $, \tau =MB\sin \theta =0.65\times 0.25\times \sin 30^o$
$=0.65\times 0.25\times \dfrac{1}{2}=0.08125=0.081\ Nm$

So, option $(C)$ is correct. 

A bar magnet has a magnetic moment of $200 A m^2$. The magnet is suspended in a magnetic field of $0.30 N A^{-1} m^{-1}$. The torque required to rotate the magnet from its equilibrium position through an angle of $30^0$, will be then

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. $30$Nm

  2. $30 \sqrt3$Nm

  3. $60$Nm

  4. $60 \sqrt3$Nm

Show answer
Correct Option: A
Explanation:

Torque experienced by a magnet suspended in a uniform magnetic field B is given by
$T = MB sin \theta$
Here, $M = 200 A m^2, B = 0.30 N A^{-1}m^{-1}  and \  \theta = 30^0$
$\therefore T = 200 \times 0.30 \times sin 30^0$
$T = 30 N m$

A magnetic needle kept non parallel to the magnetic field in a non uniform magnetic field experience.

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. A force but not a torque

  2. A torque but not a force

  3. Both a force and a torque

  4. Neither a force nor a torque

Show answer
Correct Option: C
Explanation:

Magnetic needle can be considered as a magnetic dipole since it is placed in a non uniform magnetic field it will experience af force as magnetic force on both magnetic force will be different. Also, needle is placed non parallel to the field, so it will experience a torque also.

Therefore, C is correct option. 

A uniform horizontal magnetic field of $7.5\times 10^{-2}$T is set up at angle of $30^o$ with the axis of an solenoid and the magnetic moment associated with it is $1.28$J $T^{-1}$. Then the torque on it is?

force and torque on a current carrying rectangular loop in a uniform magnetic field torque on current carrying loop force on current carrying conductor magnetic effects of current and magnetism physics

  1. $4.8\times 10^{-2}$N m

  2. $1.6\times 10^{-2}$N m

  3. $1.2\times 10^{-2}$N m

  4. $4.8\times 10^{-4}$N m

Show answer
Correct Option: A
Explanation:

Torque, $\tau =MB\sin\theta$
Here, $M=1.28J$ $T^{-1}$, $B=7.5\times 10^{-2}T, \theta =30^o$
$\therefore \tau =1.28\times 7.5\times 10^{-2}\sin 30^o$
$=1.28\times 7.5\times 10^{-2}\times \dfrac{1}{2}$
$=0.64\times 7.5\times 10^{-2}=4.8\times 10^{-2}$N m.

Fill in the blank space by choosing the correct word. 
The non-usable animal or vegetable products are collectively called ............

physics sources of energy biogas environmental use of microorganism microbes in waste treatment and biogas

  1. $potential$

  2. $renewable$

  3. $fossil$

  4. $biomass$

Show answer
Correct Option: D
Explanation:

Biomass is biological material derived from living, or recently living organisms. In the context of biomass for energy this is often used to mean plant based material, but biomass can equally apply to both animal and vegetable derived material.
Hence, the non-usable animal or vegetable products are collectively called Biomass.

Choose the correct answer from the alternatives given.
Radio waves diffract around building although light waves do not. The reason is that radio waves

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. travel with speed larger than c

  2. have much larger wavelength than light

  3. are not electromagnetic waves

  4. None of these

Show answer
Correct Option: B
Explanation:

$Answer:-$ B

Both radio and light waves are EM waves, just in different frequency ranges. The wavelength of visible light is typically around the 600 nm range, which is 6/1000 of a millimeter (very small!). Radio waves on the other hand, often wave wavelengths of a few yards long. For a wave to diffract around an object, the size of the object must be on the same order of the wavelength of the wave.

Which of the following electromagnetic wave play an important role in maintaining the earths warmth or average temperature through the greenhouse effect? 

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. Visible rays

  2. Infrared waves

  3. Gamma rays

  4. Ultraviolet rays

Show answer
Correct Option: B
Explanation:

Infrared radiation play an important role in maintaining the earths warmth or average temperature through the greenhouse effect.

The correct option is B.

The waves used by artificial satellites for communication is the

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. microwaves

  2. infrared waves

  3. radio waves

  4. X-rays

Show answer
Correct Option: A
Explanation:

The microwaves are preferred in order to communicate with the artificial satellites which are orbiting the earth at a particular height from the surface of the earth. The microwaves are preferred because they can penetrate through the Earth's atmosphere very easily and reach the target satellite.

Choose the correct answer from alternatives given.
The phenomena involved in the reflection of radio waves by ionosphere is similar to

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. reflection of light by a plane mirror.

  2. total internal reflection of light in air during a mirage.

  3. dispersion of light by water molecules during the formation of a rainbow.

  4. scattering of light by the particles of air.

Show answer
Correct Option: C
Explanation:

The phenomenon involved in the reflection of radiowaves by ionosphere is similar to total internal reflection of light in air during a mirage (angle of incidence gt critical angle). It is same as the formation of the rainbow because it also involves the process of total internal reflection.


Choice $(b)$ is correct.