List of top Questions asked in JEE Main

In an experiment of CE configuration of n–p–n transistor, the transfer characteristics are observed as given in figure. 

In an experiment of CE configuration of n–p–n transistor

If the input resistance is 200 Ω and output resistance is 60 Ω, the voltage gain in this experiment will be______.

A mass of \(10\) kg is suspended vertically by a rope of length \(5\) m from the roof. A force of \(30\) N is applied at the middle point of rope in horizontal direction. The angle made by upper half of the rope with vertical is \(θ\) = \(tan^{–1} (x × 10^{–1})\). The value of \(x\) is _______.(Given, \(g = 10\; m/s^2\))
Two point charges A and B of magnitude \(+8 \times 10^{–6} C\) and \(-8 \times 10^{–6} C\) respectively are placed at a distance d apart. The electric field at the middle point O between the charges is \(6.4 \times 10^{4} NC^{–1}\). The distance ‘d’ between the point charges A and B is:
When a gas filled in a closed vessel is heated by raising the temperature by 1ºC, its pressure increases by 0.4%. The initial temperature of the gas is _____ K.
Two long current carrying conductors are placed parallel to each other at a distance of 8 cm between them. The magnitude of magnetic field produced at mid-point between the two conductors due to current flowing in them is 30 μT. The equal current flowing in the two conductors is:
A transistor is used in an amplifier circuit in common emitter mode. If the base current changes by 100μA, it brings a change of 10mA in collector current. If the load resistance is 2kΩ and input resistance is 1kΩ, the value of power gain is \(x×10^4\). The value of x is _______.
The percentage decrease in the weight of a rocket, when taken to a height of 32 km above the surface of earth will, be:
(Radius of earth = 6400 km)
Two point charges Q each are placed at a distance d apart. A third point charge q is placed at a distance x from mid-point on the perpendicular bisector. The value of x at which charge q will experience the maximum Coulombs force is :
The activity of a radioactive material is 2.56 × 10–3 Ci. If the half life of the material is 5 days, after how many days the activity will become 2 × 10–5 Ci?
An object of mass 5 kg is thrown vertically upwards from the ground. The air resistance produces a constant retarding force of 10 N throughout the motion. The ratio of time of ascent to the time of descent will be equal to [Use \(g\) = \(10 \;ms^{–2}\)].
Given below are two statements.
Statement-I: The law of gravitation holds good for any pair of bodies in the universe.
Statement-II: The weight of any person becomes zero when the person is at the centre of the earth.
In the light of the above statements, choose the correct answer from the options given below
300 cal. of heat is given to a heat engine and it rejects 225 cal. of heat. If source temperature is 227°C, then the temperature of sink will be _______°C.
Two blocks of masses 10 kg and 30 kg are placed on the same straight line with coordinates(0, 0) cm and (x, 0) cm respectively. The block of 10 kg is moved on the same line through a distance of 6 cm towards the other block. The distance through which the block of 30 kg must be moved to keep the position of Centre of mass of the system unchanged is
Which is the correct ascending order of wavelengths?
Which of the following statement is correct ?
Two light beams of intensities in the ratio of 9 : 4 are allowed to interfere. The ratio of the intensity of maxima and minima will be:
The equivalent resistance between points A and B in the given network is:
 equivalent resistance between points A and B in the given network

Choose the correct answer:

1. Two balls A and B are placed at the top of 180 m tall tower. Ball A is released from the top at t = 0 s. Ball B is thrown vertically down with an initial velocity u at t = 2 s. After a certain time, both balls meet 100 m above the ground. Find the value of u in ms–1 [use g = 10 ms–2]

Two coils require 20 minutes and 60 minutes respectively to produce same amount of heat energy when connected separately to the same source. If they are connected in parallel arrangement to the same source; the time required to produce same amount of heat by the combination of coils, will be ___ min.
At time t = 0 a particle starts travelling from a height \(7\hat z cm\) in a plane keeping \(z\) coordinate constant. At any instant time it's position along the \(x\) and \(y\) directions are defined as \(3t\) and \(5t^3\) respectively. At \(t = 1s\) acceleration of the particle will be
Sun light falls normally on a surface of area \(36 cm^2\) and exerts an average force of \(7.2 × 10^{–9} N\) within a time period of \(20 minutes\). Considering a case of complete absorption, the energy flux of incident light is

The current density in a cylindrical wire of radius \(r = 4.0\) mm is \(1.0 \times 10^6\) \(A/m^2\). The current through the outer portion of the wire between radial distances \(\frac{r}{2}\) and \(r\) is \(xπ\) \(A\); where \(x\) is _________.

A disc with a flat small bottom beaker placed on it at a distance R from its center is revolving about an axis passing through the center and perpendicular to its plane with an angular velocity ω. The coefficient of static friction between the bottom of the beaker and the surface of the disc is μ. The beaker will revolve with the disc if :
The difference of speed of light in the two media A and B(υA – υB) is 2.6 × 107 m/s. If the refractive index of medium B is 1.47, then the ratio of refractive index of medium B to medium A is: (Given: speed of light in vacuum C = 3 × 108 ms–1)
Two parallel, long wires are kept 0.20 m apart in vacuum, each carrying current of x A in the same direction. If the force of attraction per meter of each wire is \(2 \times 10^{–6} \text{N}\), then the value of x is approximately: