JEE Main Practice Test- 20 - JEE MCQ
30 Questions MCQ Test - JEE Main Practice Test- 20
A resistance of 40 ohm and an inductance of 95.5 millihenry are connected in series in a 50 cycles/second A.C. circuit. The impedance of this combination is very nearly
A coil of 40 H inductance is connected in series with a resistance of 8 Ω and the combination is joined to the terminals of a 2 V battery. The time-constant of the circuit is
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An object of mass 10 kg is whirled round a horizontal circle of radius 4 m by a revolving string inclined 30º to the vertical. If the uniform speed of the object is 5 ms⁻1, the tension in the string is
The innermost orbit of the hydrogen atom has a diameter 1.06 Å. The diameter of tenth orbit is
For the production of X-rays, the target should be made of
An electric dipole is placed along the X-axis at the origin O. A point P is at a distance of 20 cm from this origin such that OP makes an angle π/3 with the X axis. If electric field at P makes an angle θ with X-axis, the value of θ is
Two charged conducting spheres of radii a and b are connected to each other by a wire. The ratio of electric fields at the surface of two spheres is
A lift is moving upward with increasing speed with acceleration 'a'. The apparent weight will be
If the coefficient of friction between the tyres and the road is 0.4, then maximum speed of a car on a road-turn of radius 30 m, will be
Two NOT gates are connected at the two inputs of a NAND gate. This combination will behave like
A long solenoid has a radius a and number of turns per unit length is n. If it carries a current I, then the magnetic field on its axis is directly propotional to
A horizontal pipe line carries water in a streamline flow. At a point along the pipe where cross-sectional area is 10 cm2, the velocity of water is 1 m-s⁻1 and pressure is 2000 Pa. The pressure of water, at another point where cross-sectional area is 5 cm2, is (Density of water = 1000 kg-m⁻3)
A particle has an initial velocity of 3 i ‸ + 4 j ‸ and an acceleration of 0.4 i ‸ + 0.3 j ‸ . Its speed after 10s is-
If in a nuclear reactor using U235 as fuel, the power output is 4.8 mega watts, the number of fissions per second is:
(energy released per fission of U235 = 200 MeV; 1eV = 1.6 x 10 − 19 J)
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A): Air quickly leaking out of a balloon becomes cooler.
Reason(R): The leaking air undergoes adiabatic expansion. Reason(R): The leaking air undergoes adiabatic expansion.
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A):If the string of a descending lift is broken, then it will fall down like a free body.
Reason(R):The acceleration of a free body is always 'g'.
A circular disc is rotating with angular velocity ω. A man sitting at the edge walks towards the centre of disc, then the angular velocity ω
During an adiabatic process, the pressure of a gas is proportional to the cube of its adiabatic temperature. The value of 
for that gas is
The maximum number of possible interference maxima for slit-separation equal to twice the wavelength in Young's double-slit experiment, is
Two identical light waves, propagating in the same direction, have a phase difference δ . After they superpose the intensity of the resulting wave will be proportional to
When exposed to sunlight, thin films of oil on water often exhibit brilliant colours due to the phenomenon of
The transition from the state n = 4 to n = 3 in hydrogen like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from-
A capacitor of capacity C₁ is charged by connecting it across a battery of e.m.f. V₀. The battery is then removed and the capacitor is connected in parallel with an uncharged capacitor of capacity C₂. The potential difference across this combination is
If a particle of mass m is projected from the lowest point of smooth vertical circle of radius 'A' with velocity 5 a g the pressure at its lowest point will be—
A series combination of two resistors 1 Ω each is connected to a 12 V battery of internal resistance 0.4Ω. The current flowing through it is
The figure to the right shows an edge-on view of three extremely large, parallel insulating sheets positively charged with uniform and identical surface charge densities. In which of the regions shown is the electric field a maximum?
A straight wire of diameter 0.5 mm carrying a current of 1 A is replaced by another wire of 1 mm diameter carrying the same current. The strength of magnetic field far away is
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