Practice Questions

Q27.The coercivity of a magnet is 5 × 103 A/m . The amount of current required to be passed in a solenoid of length 30 cm and the number of turns 150 , so that the magnet gets demagnetised when inside the solenoid is _____A.

Q27.A regular polygon of 6 sides is formed by bending a wire of length 4 π meter. If an electric current of 4𝜋√3 A is flowing through the sides of the polygon, the magnetic field at the centre of the polygon would be 𝑥× 10-7 T . The value of 𝑥 is ______.

Q27.A solenoid of length 0.5 m has a radius of 1 cm and is made up of ' m ' number of turns. It carries a current of 5 A . If the magnitude of the magnetic field inside the solenoid is 6.28 × 10−3 T then the value of m is _____.

Q27.A ceiling fan having 3 blades of length 80 cm each is rotating with an angular velocity of 1200 rpm. The magnetic field of earth in that region is 0. 5 G and angle of dip is 30°. The emf induced across the blades is Nπ × 10−5 V . The value of N is _______.

Q27.A moving coil galvanometer has 100 turns and each turn has an area of 2 . 0 cm2 . The magnetic field produced by the magnet is 0 . 01 T and the deflection in the coil is 0 . 05 radian when a current of 10 mA is JEE Main 2024 (01 Feb Shift 2) JEE Main Previous Year Paper passed through it. The torsional constant of the suspension wire is 𝑥× 10-5 N - m / rad . The value of 𝑥 is ______ .

Q28.When a coil is connected across a 20 V dc supply, it draws a current of 5 A. When it is connected across 20 V, 50 Hz ac supply, it draws a current of 4 A. The self inductance of the coil is ______ mH . ( Take π = 3 )

Q28.A square loop of side 10 cm and resistance 0. 7 Ω is placed vertically in the east-west plane. A uniform magnetic field of 0. 20 T is set up across the plane in the north-east direction. The magnetic field is decreased to zero in 1 s at a steady rate. Then, the magnitude of induced emf is √x × 10−3 V . The value of x is _______.

Q28.For a given series LCR circuit it is found that maximum current is drawn when value of variable capacitance is 25nF. If resistance of 200Ω and 100mH inductor is being used in the given circuit. The frequency of ac source is ______ ×103 Hz . (given π2 = 10 )

Q28.A straight magnetic strip has a magnetic moment of 44Am2 . If the strip is bent in a semicircular shape, its magnetic moment will be _______ Am2 . (given π = 227 )

Q28.In the given figure, the charge stored in 6μF capacitor, when points A and B are joined by a connecting wire is _______ μC. o

Q28.A coil of 200 turns and area 0 . 20 m2 is rotated at half a revolution per second and is placed in uniform magnetic field of 0 . 01 T perpendicular to axis of rotation of the coil. The maximum voltage generated in the 2𝜋 coil is volt. The value of 𝛽 is ______. 𝛽 ∘

Q28.An alternating emf E = 110√2 sin 100t volt is applied to a capacitor of 2μF, the rms value of current in the circuit is _____ mA ,

Q28.A series LCR circuit with 𝐿= 100 mH, 𝐶= 10-3 F and 𝑅= 10 Ω, is connected across an AC source of 𝜋 𝜋 220 V, 50 Hz supply. The power factor of the circuit would be ____. o

Q28.A alternating current at any instant is given by i = [6 + √56 sin(100πt + π/3)] A. The rms value of the current is ________ A.

Q28.Two coils have mutual inductance 0. 002 H. The current changes in the first coil according to the relation i = i0sinωt, where i0 = 5 A and ω = 50π rad s−1 . The maximum value of emf in the second coil is απ V . The value of α is

Q28.When a dc voltage of 100 V is applied to an inductor, a dc current of 5 A flows through it. When an ac voltage of 200 V peak value is connected to inductor, its inductive reactance is found to be 20√3Ω. The power dissipated in the circuit is _______ W.

Q28.The current of 5 A flows in a square loop of sides 1 m is placed in air. The magnetic field at the centre of the loop is X√2 × 10-7 T. The value of X is _________.

Q28.The horizontal component of earth's magnetic field at a place is 3. 5 × 10−5 T. A very long straight conductor carrying current of √2 A in the direction from South east to North West is placed. The force per unit length experienced by the conductor is ________ ×10−6 N m−1 .

Q29.A capacitor of reactance 4√3Ω and a resistor of resistance 4Ω are connected in series with an ac source of peak value 8√2 V . The power dissipation in the circuit is ________ W.

Q29.A parallel beam of monochromatic light of wavelength 600 nm passes through single slit of 0.4 mm width. Angular divergence corresponding to second order minima would be ______ ×10−3rad.

Q29.In a double slit experiment shown in figure, when light of wavelength 400 nm is used, dark fringe is observed at P . If D = 0. 2 m, the minimum distance between the slits S1 and S2 is α mm . Write the value of 10α to the nearest integer. JEE Main 2024 (29 Jan Shift 1) JEE Main Previous Year Paper

Q29.Two immiscible liquids of refractive indices 8 and 3 respectively are put in a beaker as shown in the figure. 5 2 The height of each column is 6 cm . A coin is placed at the bottom of the beaker. For near normal vision, the apparent depth of the coin is α 4 cm . The value of α is _______.

Q29.In a single slit diffraction pattern, a light of wavelength 6000 A is used. The distance between the first and third minima in the diffraction pattern is found to be 3 mm when the screen is placed 50 cm away from slits. The width of the slit is ____ ×10−4 m .

Q29.In a Young's double slit experiment, the intensity at a point is ( 14 )th of the maximum intensity, the minimum distance of the point from the central maximum is ________ μm . (Given : λ = 600 nm, d = 1.0 mm, D = 1.0 m )

Q29.A power transmission line feeds input power at 2 . 3 kV to a step down transformer with its primary winding having 3000 turns. The output power is delivered at 230 V by the transformer. The current in the primary of the transformer is 5 A and its efficiency is 90%. The winding of transformer is made of copper. The output current of transformer is ____A.