AC Basics: Peak, RMS & Average Values
An AC source rated 220 V, 50 Hz is connected to a resistor. The time taken by the current to change from its maximum to the rms value is:
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Answer: (a)
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JEE Main · Previous year paper · Physics
These are the 28 physics questions of JEE Main 2021 (18 Mar, Shift 1) that are in the Physics Circle question bank, arranged chapter by chapter. Tap an option to check your answer; every question links to its full solution.
AC Basics: Peak, RMS & Average Values
An AC source rated 220 V, 50 Hz is connected to a resistor. The time taken by the current to change from its maximum to the rms value is:
Answer: (a)
Full solution and similar questions →Resonance, Bandwidth & Q Factor
In a series LCR resonance circuit, if we change the resistance only, from a lower to higher value:
Answer: (a)
Full solution and similar questions →Bohr Model: Orbits, Speed & Angular Momentum
Imagine that the electron in a hydrogen atom is replaced by a muon (). The mass of muon particle is 207 times that of an electron and charge is equal to the charge of an electron. The ionization potential of this hydrogen atom will be:
Answer: (b)
Full solution and similar questions →Capacitors in DC Circuits & RC
The circuit shown in the figure consists of a charged capacitor of capacity 3 F and a charge of 30 C. At time t = 0, when the key is closed, the value of current flowing through the 5 M resistor is 'x' -A. The value of 'x' to the nearest integer is ___________.

Numerical answer type. Work it out, then open the answer.
Dielectrics
A parallel plate capacitor has plate area 100 m2 and plate separation of 10 m. The space between the plates is filled up to a thickness 5 m with a material of dielectric constant of 10. The resultant capacitance of the system is 'x' pF.
The value of 0 = 8.85 1012 F.m.
The value of 'x' to the nearest integer is _____________.
Numerical answer type. Work it out, then open the answer.
Answer: 161
Full solution and similar questions →Kirchhoff's Laws & Measuring Instruments
The voltage across the 10 resistor in the given circuit is x volt.

The value of 'x' to the nearest integer is _________.
Numerical answer type. Work it out, then open the answer.
Answer: 70
Full solution and similar questions →Matter Waves: de Broglie Wavelength
A particle is travelling 4 time as fast as an electron. Assuming the ratio of de-Broglie wavelength of a particle to that of electron is 2: 1, the mass of the particle is:
Answer: (d)
Full solution and similar questions →Nature of EM Waves & Wave Equation
A plane electromagnetic wave of frequency 100 MHz is travelling in vacuum along the x-direction. At a particular point in space and time, . (where, is unit vector along z-direction) What is at this point?
Answer: (c)
Full solution and similar questions →Motion of Charges in an Electric Field
An oil drop of radius 2 mm with a density 3g cm is held stationary under a constant electric field 3.55 105 V m in the Millikan's oil drop experiment. What is the number of excess electrons that the oil drop will possess? (consider g = 9.81 m/s2)
Answer: (b)
Full solution and similar questions →Satellites - Orbital Velocity & Period
The time period of a satellite in a circular orbit of radius R is T. The period of another satellite in a circular orbit of radius 9R is:
Answer: (b)
Full solution and similar questions →Law of Equipartition of Energy
What will be the average value of energy along one degree of freedom for an ideal gas in thermal equilibrium at a temperature T? (kB is Boltzmann constant)
Answer: (a)
Full solution and similar questions →Inertia, First & Second Laws
A bullet of mass 0.1 kg is fired on a wooden block to pierce through it, but it stops after moving a distance of 50 cm into it. If the velocity of bullet before hitting the wood is 10 m/s and it slows down with uniform deceleration, then the magnitude of effective retarding force on the bullet is 'x' N. The value of 'x' to the nearest integer is __________.
Numerical answer type. Work it out, then open the answer.
Answer: 10
Full solution and similar questions →Young's Modulus & Elongation
Two separate wires A and B are stretched by 2 mm and 4 mm respectively, when they are subjected to a force of 2 N. Assume that both the wires are made up of same material and the radius of wire B is 4 times that of the radius of wire A. The length of the wires A and B are in the ratio of a: b. Then a/b can be expressed as 1/x where x is _________.
Numerical answer type. Work it out, then open the answer.
Answer: 32
Full solution and similar questions →Graphs of Motion
The position, velocity and acceleration of a particle moving with a constant acceleration can be represented by:
Answer: (b)
Full solution and similar questions →Ampere's Law, Cylinders, Solenoid & Toroid
Four identical long solenoids A, B, C and D are connected to each other as shown in the figure. If the magnetic field at the center of A is 3T, the field at the center of C would be: (Assume that the magnetic field is confined with in the volume of respective solenoid).

Answer: (d)
Full solution and similar questions →Force on Current-Carrying Conductors
A loop of flexible wire of irregular shape carrying current is placed in an external magnetic field. Identify the effect of the field on the wire.
Answer: (a)
Full solution and similar questions →Law of Radioactive Decay
A radioactive sample disintegrates via two independent decay processes having half lives and respectively. The effective half-life T1/2 of the nuclei is:
Answer: (c)
Full solution and similar questions →Periodic Motion & SHM Basics
A particle performs simple harmonic motion with a period of 2 second. The time taken by the particle to cover a displacement equal to half of its amplitude from the mean position is s. The value of 'a' to the nearest integer is _________.
Numerical answer type. Work it out, then open the answer.
Relative Velocity in Two Dimensions
A person is swimming with a speed of 10 m/s at an angle of 120 with the flow and reaches to a point directly opposite on the other side of the river. The speed of the flow is 'x' m/s. The value of 'x' to the nearest integer is __________.
Numerical answer type. Work it out, then open the answer.
Optical Instruments & the Eye
Your friend is having eye sight problem. She is not able to see clearly a distant uniform window mesh and it appears to her as non-uniform and distorted. The doctor diagnosed the problem as:
Answer: (b)
Full solution and similar questions →Angular Momentum & its Conservation
A thin circular ring of mass M and radius r is rotating about its axis with an angular speed . Two particles having mass m each are now attached at diametrically opposite points. The angular speed of the ring will become:
Answer: (c)
Full solution and similar questions →Junction Transistor
An npn transistor operates as a common emitter amplifier with a power gain of 106. The input circuit resistance is 100 and the output load resistance is 10 K. The common emitter current gain '' will be ________. (Round off to the Nearest Integer).
Numerical answer type. Work it out, then open the answer.
Answer: 100
Full solution and similar questions →P-V Diagrams & Cyclic Processes
The P-V diagram of a diatomic ideal gas system going under cyclic process as shown in figure. The work done during an adiabatic process CD is (use = 1.4):

Answer: (a)
Full solution and similar questions →Errors in Measurement
In the experiment of Ohm's law, a potential difference of 5.0 V is applied across the end of a conductor of length 10.0 cm and diameter of 5.00 mm. The measured current in the conductor is 2.00 A. The maximum permissible percentage error in the resistivity of the conductor is:
Answer: (a)
Full solution and similar questions →Errors in Measurement
The time period of a simple pendulum is given by . The measured value of the length of pendulum is 10 cm known to a 1mm accuracy. The time for 200 oscillations of the pendulum is found to be 100 second using a clock of 1s resolution. The percentage accuracy in the determination of 'g' using this pendulum is 'x'. The value of 'x' to be nearest integer is :-
Answer: (b)
Full solution and similar questions →YDSE: Fringe Width & Fringe Positions
In Young's double slit arrangement, slits are separated by a gap of 0.5 mm, and the screen is placed at a distance of 0.5 m from them. The distance between the first and the third bright fringe formed when the slits are illuminated by a monochromatic light of 5890 is :-
Answer: (b)
Full solution and similar questions →Conservation of Energy
As shown in the figure, a particle of mass 10 kg is placed at a point A. When the particle is slightly displaced to its right, it starts moving and reaches the point B. The speed of the particle at B is x m/s. (Take g = 10 m/s2)
The value of 'x' to the nearest integer is __________.

Numerical answer type. Work it out, then open the answer.
Answer: 10
Full solution and similar questions →Power
A constant power delivering machine has towed a box, which was initially at rest, along a horizontal straight line. The distance moved by the box in time 't' is proportional to :-
Answer: (b)
Full solution and similar questions →