25 Jan 2022: UPSC Exam Comprehensive News Analysis
CNA 25 Jan 2022:- Download PDF Here TABLE OF CONTENTS A. GS 1 Related B. GS 2 Related HEALTH 1.... View Article
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International Relations This Week: Episode 58
International relations is a very important segment of the UPSC syllabus. In this series, we present an analysis of the most... View Article
A moving coil galvanometer can be converted into an ammeter by: (a) Introducing the shunt resistance of large value in series (b) introducing the shunt resistance of small value in parallel (c) introducing the resistance of small value in series (d) introducing the resistance of large value in parallel
The correct answer is (b) introducing the shunt resistance of small value in parallel Solution A galvanometer is an instrument that... View Article
A string is stretched between fixed points separated by 75 cm. It is observed to have resonant frequencies of 420 Hz and 315 Hz. There are no other resonant frequencies between these two. Then, the lowest resonant frequency for this string is
Frequency The definition of frequency, we can understand that if a body is in periodic motion, it has undergone one... View Article
A resistance wire connected in the left gap of a metre bridge balances a 10ω resistance in the right gap at a point which divides the bridge wire in the ratio 3:2. If the length of the resistance wire is 1.5m, then the length of 1ω of the resistance wire is_________
A meter bridge also called a slide wire bridge is an instrument that works on the principle of a Wheatstone... View Article
Photoelectric effect supports quantum nature of light because: (a) There is a minimum frequency of light below which no photoelectrons are emitted. (b) The maximum kinetic energy of the photoelectrons depends only on the frequency of the light and not on its intensity. (c) Even when the metal surface is faintly illuminated, the photoelectrons leave the surface immediately. (d) Electric charge of the photoelectrons is quantized.
The correct answer is(a) There is a minimum frequency of light below which no photoelectrons are emitted.(b) The maximum kinetic energy of... View Article
The intensity at the maximum in a Young’s double slit experiment is I0 . Distance between two slits is d=5λ, where λ is the wavelength of light used in the experiment. What will be the intensity in front of one of the slits on the screen placed at a distance D=10 d?
From the double slit experiment we get to know that Path difference = S2P – S1P \(\begin{array}{l}sqrt{(D^{2}+d^{2})-D}\end{array} \) = \(\begin{array}{l}D(1+frac{1}{2}frac{d^{2}}{D^{2}}-1)\end{array} \)... View Article
The heavier block is an Atwood machine that has a mass twice that of the lighter one. The tension in the string is 16.0N when the system is set into the motion. Find the decrease in the gravitational potential energy during the first second after the system is released from rest.
Tension is a force along the length of a medium, especially a force carried by a flexible medium, such as... View Article
Three identical particles are joined together by a thread as shown in figure .All the 3 particles are moving in a horizontal plane .if the velocity of the outermost particle isV○ ,then the ratio of tension in the three section of the string (a)3:5:7 (b) 3:4:5 (c)7:11:6 (d) 3:5:6
Solution As per the given data angular velocity ω is same for all Tc=mω2(3ℓ) TB=Tc+mω2(2ℓ)= mω2(5ℓ) TA=TB+mω2(ℓ)= mω2(6ℓ) ∴Tc:TB:TA::3:5:6 Answer The ratio... View Article
In a double slit experiment, the two slits are 1 mm apart and the screen is place 1 m away. A monochromatic light of wavelength 500 nm is used. What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of single slit pattern?
Least Common Multiple (LCM) is a way of finding the smallest common multiple between any two numbers or more. A... View Article
Two towns A and B are connected by regular bus service with a bus leaving in either direction every T minutes. A man cycling with a speed of 20 km h–1 in the direction A to B notices that a bus goes past him every 18 min in the direction of his motion, and every 6 min in the opposite direction. What is the period T of the bus service and with what speed (assumed constant) do the buses ply on the road?
Solution Given that Speed of the cyclist = 20 km/h A bus goes past him every 18 min in the direction... View Article
If two liquids A and B form minimum boiling azeotrope at some specific composition then: (A) A-B interactions are stronger than those between A-A or B-B. (B) vapour pressure of solution increases because more molecules of liquids A and B can escape from the solution. (C) vapour pressure of solution decreases because less number of molecules of liquids A and B can escape from the solution. (D) show a large positive deviation from Raoult’s law.
The corrct answer is (D) show a large positive deviation from Raoult’s law. Answer Raoult’s law Raoult’s law states that a... View Article
Two particles are oscillating along two close parallel straight lines side by side, with the same frequency and amplitudes. They pass each other, moving in opposite direction when their displacement is half of the amplitude. The mean positions of the two particles lie on a straight line perpendicular to the paths of the two particles. The phase difference is:
The phase difference is = 2∏/3 radians Solution Let us represent the particles by equation y1 and y2 respectively. y1... View Article
A cricket ball of mass 0.15 kg is moving with a velocity of 12 ms – 1 and is hit by a bat so that the ball is turned back with a velocity of 20 ms – 1. If the force of blow acts for 0.01 s, find the average force exerted on the ball by the bat.
Given that Initial velocity u=12 ms−1 Final velocity v=20 ms−1 Time for which force is acting, t = 0.01 s... View Article
There are 27 drops of a conducting fluid. Each drop has radius r, and each of them is charged to the same potential V1.They are then combined to form a bigger drop.The potential of the bigger drop is V2 .Find the ratio V2/V1. [Ignore the change in density of the fluid on combining the drops].
Answer: Let Charge on each drop = q Charge on big drop = Q = 27q Radius of bigger drop... View Article
A thin rectangular magnet suspended freely has a period of oscillation equal to T. Now it is broken into two equal halves (each having half of the original length) and one piece is made to oscillate freely in the same field. if its period of oscillation is T’, the ratio T’/T is_______
Answer: A thin rectangular magnet suspended freely has a period of oscillation equal to T. Now it is broken into... View Article
A series LCR circuit is connected to an ac voltage source. When L is removed from the circuit, the phase difference between current and voltage is 3π. If instead C is removed from the circuit, the phase difference is again 3π between current and voltage. The power factor of the circuit is (1) 0.5 (2) 1.0 (3) -1.0 (4) zero
Answer:(2) 1.0 An LCR circuit is also known as a resonant circuit or tuned circuit. It consists of an inductor-L,... View Article
A positively charged particle is released from rest in an unform electric field. The electric potential energy of the charge (1) remains a constant because the electric field is uniform. (2) increases because the charge moves along the electric field. (3) decreasases because the charge moves along the electric field (4) decreases because the charge moves opposite to the electric field.
Answer: (3) decreasases because the charge moves along the electric field When a positively charged particle in a uniform field... View Article
An open pipe is in resonance in 2nd harmonic with frequency f1. Now one end of the tube is closed and frequency is increased to f2 such that the resonance again occurs in nth harmonic. Choose the correct option. (A) n = 5, f2 = (5/4)f1 (B) n = 3, f2 = (3/4)f1 (C) n =5, f2 = (3/4)f1 (D) n =3, f2 = (5/4)f1
An open pipe is in resonance in 2nd harmonic with frequency f<sub>1</sub>. Now one end of the tube is closed... View Article
A resistance R is to be measured using a meter bridge. Student chooses the standard resistance S to be 100Ω. He finds the null point at l1 = 2.9cm. He is told to attempt to improve the accuracy. Which of the following is a useful way? (1) He should measure l1 more accurately (2) He should change S to 1000Ω and repeat the experiment (3) He should change S to 3Ω and repeat the experiment (4) He should give up hope of a more accurate measurement with a meter bridge
Answer: (3) He should change S to 3Ω and repeat the experiment The balance of a metre bridge is always... View Article
