Recent questions in JEEMAIN-2016

Arrange the following electromagnetic radiations per quantum in the order of increasing energy : <br> A : Blue light B : Yellow light C : X-ray D : Radiowave

asked Mar 6, 2017 by meena.p

1 answer

An arc lamp requires a direct current of 10 A at $80\; V$ to function. It is connected to a $220 \;V(rms), 50\; Hz$ AC supply, the series inductor needed for it to work is close to :

asked Mar 6, 2017 by meena.p

1 answer

Hysteresis loops for two magnetic materials A and B are given below : These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then it is proper to use :

asked Mar 6, 2017 by meena.p

1 answer

Two identical wires A and B, each of length ‘l ’, carry the same current I. Wire A is bent into a circle of radius R and wire B is bent to form a square of side ‘a’. If $B_A$ and $B_B$ are the values of magnetic field at the centres of the circle and square respectively, then the ratio $\large\frac{B_A}{B_B}$ is :

asked Mar 6, 2017 by meena.p

1 answer

The temperature dependence of resistances of $Cu$ and undoped Si in the temperature range $300 - 400 K$ , is best described by :

asked Mar 6, 2017 by meena.p

1 answer

A combination of capacitors is set up as shown in the figure. The magnitude of the electric field due to a point charge Q (having a charge equal to the sum of the charges on the $4 \mu F$ and $9 \mu F$ capacitors), at a point distant $30\; m$ from it, would equal :

asked Mar 6, 2017 by meena.p

1 answer

The region between two concentric spheres of radii $‘a’$ and $‘b’$, respectively (see figure), has volume charge density $\rho = \large\frac{A}{r}$, where A is a constant and r is the distance from the centre. At the centre of the spheres is a point charge Q. The value of A such that the electric field in the region between the spheres will be constant, is :

asked Mar 6, 2017 by meena.p

1 answer

A uniform string of length $20\;m$ is suspended from a rigid support. A short wave pulse in introduced at its lowest end. It starts moving up the string. The time taken to reach the support is : (take $g=10\;ms^{-2})$

asked Mar 6, 2017 by meena.p

1 answer

A particle performs simple harmonic motion with amplitude A. Its speed is trebled at the instant that it is at a distance $\large\frac{2A}{3}$ from equilibrium position. The new amplitude of the motion is :

asked Mar 2, 2017 by meena.p

1 answer

‘n’ moles of an ideal gas undergoes a process $A \to B$ as shown in the figure. The maximum temperature of the gas during the process will be :

asked Mar 2, 2017 by meena.p

1 answer

An ideal gas undergoes a quasi static, reversible process in which its molar heat capacity Cremains constant. If during this process the relation of pressure P and volume V is given by $PV^n= constant$, then n is given by (Here $C_P$ and $C_V$ are molar specific heat at constant pressure and constant volume, respectively) :

asked Mar 2, 2017 by meena.p

1 answer

A pendulum clock loses $12\;s$ a day if the temperature is $40 ^{\circ} C $ and gains $4s\;a$ day if the temperature is $20 ^{\circ}C$. The temperature at which the clock will show correct time, and the co-efficient of linear expansion $(\alpha)$ of the metal of the pendulum shaft are respectively :

asked Mar 2, 2017 by meena.p

1 answer

A satellite is revolving in a circular orbit at a height ‘h’ from the earth’s surface (radius of earth R; $h << R$ ). The minimum increase in its orbital velocity required, so that the satellite could escape from the earth’s gravitational field, is close to : (Neglect the effect of atmosphere).

asked Mar 2, 2017 by meena.p

1 answer

A roller is made by joining together two cones at their vertices O.It is kept on two rails AB and CD which are placed asymmetrically (see figure), with its axis perpendicular to CD and its centre O at the centre of line joining AB and CD (see figure). It is given a light push so that it starts rolling with its centre O moving parallel to CD in the direction shown. As it moves, the roller will tend to :

asked Mar 2, 2017 by meena.p

1 answer

A person trying to lose weight by burning fat lifts a mass of $10\; kg$ upto a height of $1\; m\; 1000\;times$.Assume that the potential energy lost each time he lowers the mass is dissipated. How much fat will he use up considering the work done only when the weight is lifted up? Fat supplies $3.8 \times 10^7\;J$ of energy per kg which is converted to mechanical energy with a $20\%$ efficiency rate. Take $g = 9.8 ms^{-2}$:

asked Mar 1, 2017 by meena.p

1 answer

A point particle of mass $m$, moves along the uniformly rough track $PQR$ as shown in the figure.The coefficient of friction, between the particle and the rough track equals $\mu$. The particle is released, from rest, from the point P and it comes to rest at a point R. The energies, lost by the ball, over the parts, PQ and QR, of the track, are equal to each other, and no energy is lost when particle changes direction from PQ to QR.The values of the coefficient of friction $\mu$ and the distance $x (= QR),$ are, respectively close to :

asked Mar 1, 2017 by meena.p

1 answer

A particle of mass m is moving along the side of a square of side $‘a’$, with a uniform speed $v$ in the $x-y$ plane as shown in the figure : Which of the following statements is false for the angular momentum $\overrightarrow {L}$ about the origin?

asked Mar 1, 2017 by meena.p

1 answer

A student measures the time period of $100$ oscillations of a simple pendulum four times. The data set is $90\; s, 91\; s, 95\; s\; and\; 92\; s$. If the minimum division in the measuring clock is $1\; s$, then the reported mean time should be :

asked Mar 1, 2017 by meena.p

1 answer

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