List of top Questions asked in WBJEE- 2009

The value of integral $\int\limits_{-1}^{1} \frac{\left|x+2\right|}{x+2} dx$ is

An electrical cable having a resistance of $0.2 \,\Omega$ delivers $10\,kw$ at $200\,V\, D.C$. to a factory. What is the efficiency of transmission?

The angle between the lines joining the foci of an ellipse to one particular extremity of the minor axis is $90^{\circ}$ The eccentricity of the ellipse is

The equation $\sqrt{3}\, \sin \,x+\cos\,x = 4$ has

It is difficult to cook rice in an open vessel by boiling it at high altitudes because of

The current flowing through a wire depends on time as $I=3t^{2}+2t +5.$ The charge flowing through the cross section of the wire in time from $t = 0$ to $t = 2$ sec. is

Two identical cells each of emf $E$ and internal resistance $r$ are connected in parallel with an external resistance $R$. To get maximum power developed across $R$, the value of $R$ is

The value of $ \displaystyle\lim_{n\to\infty} \left[\frac{n}{n^{2}+1^{2}}+\frac{n}{n^{2}+2^{2}}+\ldots+\frac{1}{n^{2}+2n}\right] $ is

The modulus of $\frac{1-i}{3+i}+\frac{4i}{5}$ is

Two identical light waves, propagating in the same direction, have a phase difference $\delta$. After they superpose the intensity of the resulting wave will be proportional to

The half-life of a radioactive element is 10 hours. How much will be left after 4 hours in 1 g atom sample?

A junction diode has a resistance of 25 O when forward biased and 2500 O when reverse biased. The current in the diode, for the arrangement shown will be

Magnetic field intensity $H$ at the centre of a circular loop of radius $r$ carrying current $I$ is

One $kg$ of copper is drawn into a wire of $1$ mm diameter and a wire of $2$ mm diameter. The resistance of the two wires will be in the ratio

$19\, g$ of water at $30? C$ and $5\, g$ of ice at $- 20?\, C$ are mixed together in a calorimeter. What is the final temperature of the mixture? Given specific heat of ice = $0.5\,cal g^{-1} ?C ^{-1}$ and latent heat of fusion of ice = $80\, cal \,g^{-1}$

Which of the following materials is the best conductor of electricity?

A wire of resistance $5\,\Omega$ is drawn out so that its new length is $3$ times its original length.What is the resistance of the new wire?

A line through the point $A(2, 0)$ which makes an angle of $30^{\circ}$ with the positive direction of $x$-axis is rotated about $A$ in clockwise direction through an angle $15^{\circ}$. Then, the equation of the straight line in the new position is

The value of $\int\limits_{0}^{\infty} \frac{dx}{\left(x^{2}+4\right)\left(x^{2}+9\right)}$ is

For any two sets $A$ and $B$, $A-(A-B)$ equals

Of the following compounds the most acidic is

The catalyst used for olefin polymerization is

The monomer used to produce orlon is

If $C_{0}, C_{1}, C_{2}, \ldots, C_{n}$ denote the coefficients in the expansion of $(1+x)^{n}$, then the value of $C_{1}+2C_{2}+3C_{3}+\ldots+nC_{n}$ is

For what value of $m$, $\frac{a^{m+1}+b^{m+1}}{a^{m}+b^{m}}$ is the arithmetic mean of $�a�$ and $�b�$ ?