JEE Main 2019 January 9 Shift 2 Paper & Solutions - JEE MCQ

Ge and Si diodes start conducting at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection are reversed, the value of V_o changes by : (assume that the Ge diode has large breakdown voltage)

A rod of mass 'M' and length '2L' is suspended at its middle by a wire. It exhibits torsional oscillations; If two masses each of 'm' are attached at distance 'L/2' from its centre on both sides, it reduces the oscillation frequency by 20%. The value of ratio m/M is close to 

A 15 g mass of nitrogen gas is enclosed in a vessel at a temperature of 27°C. Amount of heat transferred to the gas, so that RMS velocity of molecules is doubled, is about :
[Take R = 8.3 J/ K mole]

A particle is executing simple harmonic motion (SHM) of amplitude A, along the x-axis, about x = 0. When its potential Energy (PE) equals kinetic energy (KE), the position of the particle will be :

A musician using an open flute of length 50 cm produces second harmonic sound waves. A person runs towards the musician from another end of a hall at a speed of 10 km/h. If the wave speed is 330 m/s, the frequency heard by the running person shall be close to :

In a communication system operating at wavelength 800 nm, only one percent of source frequency is available as signal bandwidth. The number of channels accomodated for transmitting TV signals of band width 6 MHz are (Take velocity of light c = 3 × 10⁸m/s,h = 6.6 × 10^–34 J-s)

Two point charges q₁ and  are placed on the x-axis at x = l m and x = 4 m respectively. The electric field (in V/m) at a point y = 3 m on y-axis is,

A parallel plate capacitor with square plates is filled with four dielectrics of dielectric constants K₁, K₂, K₃, K₄ arranged as shown in the figure. The effective dielectric constant K will be :

A rod of length 50cm is pivoted at one end. It is raised such that if makes an angle of 30° from the horizontal as shown and released from rest. Its angular speed when it passes through the horizontal (in rad s^–1) will be (g = 10ms^–2)

One of the two identical conducting wires of length L is bent in the form of a circular loop and the other one into a circular coil of N identical turns. If the same current is passed in both, the ratio of the magnetic field at the central of the loop (B_L) to that at the centre of the coil (B_C), i.e. R   will be :

The energy required to take a satellite to a height 'h' above Earth surface (radius of Earth = 6.4 x 10³ km) is E₁ and kinetic energy required for the satellite to be in a circular orbit at this height is E₂. The value of h for which E₁ and E₂ are equal, is:

The energy associated with electric field is (U_E) and with magnetic field is (U_B) for an electromagnetic wave in free space. Then :

A series AC circuit containing an inductor (20 mH), a capacitor (120 μF) and a resistor (60Ω) is driven by an AC source of 24 V/50 Hz. The energy dissipated in the circuit in 60 s is :

Expression for time in terms of G (universal gravitational constant), h (Planck constant) and c (speed of light) is proportional to :

The magnetic field associated with a light wave is given, at the origin, by B = B₀ [sin(3.14 × 10⁷)ct + sin(6.28 × 10⁷)ct]. If this light falls on a silver plate having a work function of 4.7 eV, what will be the maximum kinetic energy of the photo electrons ?
(c = 3 × 10⁸ms^–1, h = 6.6 × 10^–34 J-s)

Charge is distributed within a sphere of radius R with a volume charge density  where A and a are constants. If Q is the total charge of this charge distribution, the radius R is :

Two Carnot engines A and B are operated in series. The first one, A, receives heat at T₁(= 600 K) and rejects to a reservoir at temperature T₂. The second engine B receives heat rejected by the first engine and, in turn, rejects to a heat reservoir at T₃(= 400 K). Calculate the temperature T₂ if the work outputs of the two engines are equal :

A carbon resistance has a following colour code. What is the value of the resistance ?

A force acts on a 2 kg object so that its position is given as a function of time as x = 3t² + 5. What is the work done by this force in first 5 seconds ?

The position co-ordinates of a particle moving in a 3-D coordinate system is given by x = a cosωt y = a sinωt and z = aωt The speed of the particle is :

In the given circuit the internal resistance of the 18 V cell is negligible. If R₁ = 400 Ω, R₃ = 100 Ω and R₄ = 500 Ω and the reading of an ideal voltmeter across R₄ is 5V, then the value R₂ will be :

A mass of 10 kg is suspended vertically by a rope from the roof. When a horizontal force is applied on the rope at some point, the rope deviated at an angle of 45° at the roof point. If the suspended mass is at equilibrium, the magnitude of the force applied is (g = 10 ms ^–2)

In a car race on straight road, car A takes a time t less than car B at the finish and passes finishing point with a speed 'v' more than that of car B. Both the cars start from rest and travel with constant acceleration a₁ and a₂ respectively. Then 'v' is equal to

A power transmission line feeds input power at 2300 V to a step down transformer with its primary windings having 4000 turns. The output power is delivered at 230 V by the transformer. If the current in the primary of the transformer is 5A and its efficiency is 90%, the output current would be :

The top of a water tank is open to air and its water level is maintained. It is giving out 0.74 m³ water per minute through a circular opening of 2 cm radius in its wall. The depth of the centre of the opening from the level of water in the tank is close to :

The pitch and the number of divisions, on the circular scale, for a given screw gauge are 0.5 mm and 100 respectively. When the screw gauge is fully tightened without any object, the zero of its circular scale lies 3 divisions below the mean line.
The readings of the main scale and the circular scale, for a thin sheet, are 5.5 mm and 48 respectively, the thickness of this sheet is :

A particle having the same charge as of electron moves in a circular path of radius 0.5 cm under the influence of a magnetic field of 0.5 T. If an electric field of 100 V/m makes it to move in a straight path, then the mass of the particle is
(Given charge of electron =1.6 × 10^–19C)