# Archives

## Carbon Footprint & Carbon Watch

Carbon Footprint of an individual can be assessed through a mobile app, Carbon Watch.  Carbon Footprint and Carbon Watch have been in news... View Article

## National Mission of Justice Delivery and Legal Reforms

The Union Cabinet of India, on June 23, 2011, approved the proposal for a National Mission for Justice Delivery and Legal Reforms in the country.... View Article

## 16 July 2021: The Hindu Analysis

UPSC Current Affairs Preparation: The Hindu Analysis Watch expert analysis of ‘The Hindu’ dated 16th Jul 2021. Important news and views to boost... View Article

## Gist of EPW July Week 1, 2021

The Economic and Political Weekly (EPW) is an important source of study material for IAS, especially for the current affairs segment. In this... View Article

## A 2 W carbon resistor is color coded with green, black, red and brown respectively. The maximum current which can be passed through this resistor is :

a. 0.4 mA b. 20 mA c. 63 mA d. 100 mA Answer: b P = i2R For imax. R should be minimum. From colour coding R = 50×102 ohm imax= 20 mA... View Article

## A potentiometer wire AB having length L and resistance 12r is joined to a cell D of emf ε and internal resistance 3r is connected. The length AJ at which the galvanometer as shown in fig. shows no deflection is :

a. (13/24) L b. (5/12) L c. (11/24) L d. (11/12) L Answer: a Potential gradient =( ε/12r+r)×(12r/L)] =... View Article

## A TV transmission tower has a height of 140 m and the height of the receiving antenna is 40 m. What is the maximum distance upto which signals can be broad casted from this tower in LOS(Line of Sight) mode? (Given : radius of earth =6.4×106m)

a. 40 km b. 80 km c. 65 km d. 48 km Answer: c Given height of the transmission tower, ht = 140 m Height of the receiving antenna, hr = 40... View Article

## To get output ‘1’ at R, for the given logic gate circuit the input values must be :

a. X = 0, Y = 0 b. X = 0, Y = 1 c. X = 1, Y = 0 d. X = 1, Y = 1 Answer: c Q = O/P = To make O/P P+Q should be ‘O’ Hence X = 1... View Article

## Using a nuclear counter the count rate of emitted particles from a radioactive source is measured. At t = 0 it was 1600 counts per second and t = 8 seconds it was 100 counts per second. The count rate observed, as counts per second, at t = 6 seconds is close to :

a. 150 b. 200 c. 360 d. 400 Answer: b At t = 0, A0 = dN/dt = 1600 C/s At t = 8s, A = 100 C/s A/A0 = 1/16 in 8 seconds Hence half life... View Article

## In an electron microscope, the resolution that can be achieved is of the order of the wavelength of electrons used. To resolve a width of 7.5×10-12 m, the minimum electron energy required is close to :

a. 1 keV b. 25 keV c. 500 keV d. 100 keV Answer: b Given λ = 7.5×10-12 h = λ = h/P P = h/λ KE = P2/2m =... View Article

## In a Young’s double slit experiment with slit separation 0.1 mm, one observes a bright fringe at angle 1/40 rad by using light of wavelength λ1. When the light of wavelength λ2 is used a bright fringe is seen at the same at the same angle in the same set up. Given that λ1 and λ2 are in visible range (380 nm to 740 nm), their values are :

a. 380 nm, 525 nm b. 625 nm, 500 nm c. 380 nm, 500 nm d. 400 nm, 500 nm Answer: b Path difference = d sinθ = dθ (approx) =... View Article

## A plano convex lens of refractive index μ1 and focal length f1 is kept in contact with another plano concave lens of refractive index μ2 and focal length f2. If the radius of curvature of their spherical faces is R each and f1 = 2f2, then μ1 and μ2 are related as :

a. μ1 + μ2 = 3 b. 2μ2- μ1 = 1 c. 2μ1- μ2 = 1 d. 3μ2- 2μ1 = 1 Answer: c Given f1 = 2f2 (1/2f2) = (1/f1) =... View Article

## If the magnetic field of a plane electromagnetic wave is given by (The speed of light =3×108 m/sec) $B = 100times 10^{-6}sin left ( 2pi times 2times 10^{15} (t-frac{x}{c})right )$ then the maximum electric field associated with it is

a. 4×104 N/C b. 6×104 N/C c. 3×104 N/C d. 4.5×104 N/C Answer: c E0 = B0×C = 100×10-6×3×108 = 3×104N/C... View Article

## A magnet of total magnetic moment $10^{-2}hat{i}$ A-m2 is placed in a time-varying magnetic field, $Bhat{i}(cos omega t)$ where B = 1 Tesla and ω= 0.125 rad/s. The work done for reversing the direction of the magnetic moment at t = 1 second, is

a. 0.007 J b. 0.02 J c. 0.01 J d. 0.028 J Answer: b Work done, W = = 2×10-2×1 cos(0.125) = 0.02 J... View Article

## An insulting thin rod of length l has a linear charge density $rho (x)= rho _{0}frac{x}{l}$ on it. The rod is rotated about an axis passing through the origin (x = 0) and perpendicular to the rod. If the rod makes n rotations per second, then the time averaged magnetic moment of the rod is :

a. (π/4)nρl3 b. nρl3 c. πnρl3 d. (π/3)nρl3 Answer: a Since M = NIA dq = λdx and A = πx2... View Article

## A solid metal cube of edge length 2 cm is moving in the positive y direction at a constant speed of 6 m/s. There is a uniform magnetic field of 0.1 T in the positive z direction. The potential difference between the two faces of the cube perpendicular to the x axis, is :

a. 1 mV b. 6 mV c. 12 mV d. 2 mV Answer: c The potential difference between two faces perpendicular to x axis will be... View Article

## In the given circuit the cells have zero internal resistance. The currents (in Amperes) passing through resistance R1, and R2 respectively, are:

a. 2,2 b. 0,1 c. 1,2 d. 0.5,0 Answer: d i1 = 10/20 = 0.5 A i2 = 0... View Article

## A uniform metallic wire of resistance 18 ohm is bent to form an equilateral triangle. The resistance across any two vertices of the triangle is (in ohm).

a. 8 ohm b. 12 ohm c. 4 ohm d. 2 ohm Answer: c Let Req be resistance between any two vertex. 1/Req = (1/12)+(1/6) So Req = 4 ohm... View Article

## A charge Q is distributed over three concentric spherical shells of radii a, b, c (a< b < c) such that their surface charge densities are equal to one another. The total potential at a point at distance r from their common centre, where r < a, would be :

a. b. c. d. Answer: b Potential at point P, V = Since Qa : Qb : Qc : :a 2 : b2: c2 Since σa = σb = σc So Qa =... View Article

## Two electric dipoles, A,B with respective dipole moments $vec{d_{A}}=-4qahat{i}$ and $vec{d_{B}}=-2qahat{i}$ placed on the x-axis with a separation R, as shown in the figure.

The distance from A at which both of them produce the same potential is: a. b. c. d. Answer: a V = 4qa/(R+x) = 2qa/x2... View Article