1.Which of the following is / are correct statements?
- When glass rod is rubbed with silk, negative charge develops on silk
- When Ebonite rod is rubbed with fur, negative charge develops on fur
Select the correct option from the codes given below:
[A] Only 1
[B] Only 2
[C] Both 1 & 2
[D] Neither 1 nor 2
Correct Answer: A [ Only 1]
When a glass rod is rubbed with silk, a positive charge develops on the glass rod and a negative charge is developed on silk. The glass rod transfers its electrons to the silk when it is rubbed with silk. Thus, glass rod has less number of electrons than the number of protons in the nucleus. Thus, on the whole, the glass rod gets positively charged. When an ebonite rod is rubbed with fur, a negative charge develops on ebonite rod and a positive charge develops on fur. Ebonite rod gains electrons from the fur when it is rubbed with fur. Thus ebonite has more negative charges as compared to positive charges in the nucleus. Thus, on the whole, ebonite rod gets negatively charged.
2.The FM transmission of music is of very good quality in comparison to AM transmission. Consider the following statements with this reference:
- The AM signals are more susceptible to noise
- The FM receiver locks itself to catch stronger signal only
- The wavelength of AM waves is much higher in comparison to the FM waves
Which among the above is / are correct statements?
[A] Only 1 & 2
[B] Only 1
[C] Only 2 & 3
[D] 1, 2 & 3
Correct Answer: D [ 1, 2 & 3]
The first statement is correct. Signal quality is a lot superior in FM than AM because the amplitude based signals are more susceptible to noise than those which use frequency. Further, the noise signals are difficult to filter out in AM reception whereas FM receivers easily filter out noise using the capture effect and pre-emphasis, de-emphasis effects. In capture effect, the receiver locks itself to catch stronger signal so that signals received are more synced with that at the transmitting end.
In pre-emphasis, de-emphasis process, the signal is further amplified to a higher frequency at sending end (pre-emphasis) and vice versa at receiver end (de-emphasis). These two processes reduce down the chances of a signal to get mixed with other signals and make FM more immune to noise than AM.
The third statement is also correct. AM waves work in the range of KHz while in FM waves work in MHz range. As a result, AM waves have a higher wavelength than the FM ones. A higher wavelength increases the range of AM signals as compared to FM which have a limited area of coverage.
3.The X-ray crystallography mainly uses which among the following properties of electromagnetic radiation?
Correct Answer: B [ Diffraction]
X-ray crystallography helps to determine the atomic and molecular structure of a crystal. The crystalline structure performs the diffraction and it causes a beam of incident X-rays to diffract into many specific directions.
4.Which among the following orbits are more prone to harms of space debris or space Junk in comparison to others?
[A] Polar Sun Synchronous Orbit
[B] Low Earth Orbit
[C] Geosynchronous orbit
[D] Geostationary Orbit
Correct Answer: D [ Geostationary Orbit]
Because, there is only one Geostationary orbit.
5.When the white light is incident on the refracting face of the prism:
- red waves undergo least deviation
- waves with longer wavelength deviate lesser
- the phenomenon of differential deviation of rays is called dispersion
Which among the above statements is / are correct?
[A] Only 1
[B] Only 1 & 2
[C] Only 2 & 3
[D] Only 1 & 3
Correct Answer: D [ Only 1 & 3]
The phenomenon due to which white light splits up into seven colours on passing through a prism is called dispersion of light. White light is made of seven colour bands (VIBGYOR), such that the rays in each band have different wavelength and different frequencies. When the white light is incident on the refracting face of the prism each coloured ray deviates through different angle, depending upon its wavelength. The red rays deviate least, whereas the violet rays deviate most. It is this differential deviation of rays, which causes dispersion. Violet colour deviates the most.
6.Who among the following is credited for the discovery of ‘Expanding Universe’?
[A] Edwin Hubble
[B] Niels Bohr
[C] S Chandra Shekhar
[D] C.V Raman
Correct Answer: A [Edwin Hubble]
Edwin Hubble, an american astronomer, and was the first to prove that the universe is expanding. According to Expanding Universe theory, the universe is presently expanding. Hubble proved that there is a direct relationship between the speeds of distant galaxies and their distances from Earth. This is now known as Hubble’s Law.
7.Which of the following units is NOT used for measuring length?
[A] Astronomical Unit
[B] Light year
[C] Par sec
Correct Answer: D [ slug ]
Astronomical Unit, Light year and Par sec are the units used to measure very large distances whereas slug is a unit to measure heavy masses. 1 slug = 14.57 kg
8.The branch of mechanics which deals with the study of motion of material objects without taking into account the factors which cause motion is called as:
[D] None of the above
Correct Answer: B [Kinematics]
The branch of mechanics which deals with the study of motion of material objects without taking into account the factors which cause motion is called as Kinematics. The branch of mechanics which deals with the study of motion of material objects taking into account the factors which cause motion is called as Dynamics. The branch of mechanics which deals with the study of material objects at rest is called as Statics.
9.What is the angular acceleration of a body moving with constant angular velocity?
[A] equal to the angular velocity
[D] Can’t be determined
Correct Answer: C 
The angular acceleration of a body moving with constant angular velocity is 0. Angular acceleration of an object in circular motion is defined as the time rate of change of its angular velocity.
10.Which of the following is NOT correct about Vectors addition?
[A] Vectors addition is associative
[B] Vectors addition is commutative
[C] Vectors of different natures can be added
[D] None of the above
Correct Answer: C [Vectors of different natures can be added]
Vectors addition is associative and commutative. But vectors of the same nature alone can be added. Example: a Force vector cannot be added to velocity vector as they are of different nature.