Practice Questions

Q27.A 2 A current carrying straight metal wire of resistance 1Ω, resistivity 2 × 10−6Ωm , area of cross-section 10 mm2 and mass 500 g is suspended horizontally in mid air by applying a uniform magnetic field →B . The magnitude of B is _____ ×10−1 T (given, g = 10 m/s2 ). JEE Main 2024 (05 Apr Shift 1) JEE Main Previous Year Paper

Q27.An electron moves through a uniform magnetic field →𝐵= 𝐵0 ^i + 2𝐵0 ^j T. At a particular instant of time, the → velocity of electron is →𝑢= 3 ^i + 5 ^j m s-1. If the magnetic force acting on electron is 𝐹= 5𝑒 ^k N, where 𝑒 is the charge of electron, then the value of 𝐵0 is ____ T.

Q27.Two resistance of 100𝛺 and 200𝛺 are connected in series with a battery of 4 V and negligible internal resistance. A voltmeter is used to measure voltage across 100𝛺 resistance, which gives reading as 1 V. The resistance of voltmeter must be _______ 𝛺. JEE Main 2024 (30 Jan Shift 2) JEE Main Previous Year Paper

Q27.A square loop of edge length 2 m carrying current of 2 A is placed with its edges parallel to the x y axis. A magnetic field is passing through the x −y plane and expressed as →B = B0(1 + 4x)^k, where B0 = 5 T. The net magnetic force experienced by the loop is _______ N .

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 circular coil having 200 turns, 2.5 × 10−4 m2 area and carrying 100μA current→ is placed in a uniform magnetic field of 1T. Initially the magnetic dipole moment (M) was directed along →B. Amount of work, required to rotate the coil through 90∘ from its initial orientation such that M becomes perpendicular to →B, is ______ μJ.

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.Two circular coils 𝑃 and 𝑄 of 100 turns each have same radius of 𝜋 cm. The currents in 𝑃 and 𝑅 are 1 A and 2 A respectively. 𝑃 and 𝑄 are placed with their planes mutually perpendicular with their centers coincide. The resultant magnetic field induction at the center of the coils is √𝑥 mT, where 𝑥= ______. [Use 𝜇0 = 4𝜋× 10−7 T m A−1]

Q27.The magnetic field existing in a region is given by →B = 0.2(1 + 2x)^k T. A square loop of edge 50 cm carrying 0.5 A current is placed in x −y plane with its edges parallel to the x −y axes, as shown in figure. The magnitude of the net magnetic force experienced by the loop is_____ mN .

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.The magnetic potential due to a magnetic dipole at a point on its axis situated at a distance of 20 cm from its center is 1. 5 × 10−5 T m . The magnetic moment of the dipole is _______ A m2 . (Given : μ0 = 10−7 T m A−1 ) 4π

Q27.A coil having 100 turns, area of 5 × 10−3 m2 , carrying current of 1 mA is placed in uniform magnetic field of 0.20 T such a way that plane of coil is perpendicular to the magnetic field. The work done in turning the coil through 90∘ is _______ μJ.

Q27.An electron with kinetic energy 5eV enters a region of uniform magnetic field of 3 μT perpendicular to its direction. An electric field E is applied perpendicular to the direction of velocity and magnetic field. The value of E , so that electron moves along the same path, is _______ NC−1 . ( Given, mass of electron = 9 × 10−31 kg , electric charge = 1.6 × 10−19C)

Q27.To determine the resistance (R) of a wire, a circuit is designed below. The V −I characteristic curve for this circuit is plotted for the voltmeter and the ammeter readings as shown in figure. The value of R is ______ Ω.

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 ______ .

Q27.A horizontal straight wire 5 m long extending from east to west falling freely at right angle to horizontal component of earth's magnetic field 0. 60 × 10−4 Wb m−2 . The instantaneous value of emf induced in the wire when its velocity is 10 m s−1 is _______ ×10−3 V . JEE Main 2024 (29 Jan Shift 2) JEE Main Previous Year Paper

Q27.Two long, straight wires carry equal currents in opposite directions as shown in figure. The separation between the wires is 5. 0 cm. The magnitude of the magnetic field at a point P midway between the wires is _____ μT . (Given: μ0 = 4π × 10−7 T m A−1 )

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.Two parallel long current carrying wire separated by a distance 2r are shown in the figure. The ratio of magnetic field at A to the magnetic field produced at C is x . The value of x is _____ 7

Q27.The magnetic field at the centre of a wire loop formed by two semicircular wires of radii 𝑅1 = 2𝜋 m and 𝑅2 = 4𝜋 m carrying current 𝐼= 4 A as per figure given below is 𝛼× 10-7 T. The value of 𝛼 is _____. (Centre O is common for all segments) JEE Main 2024 (27 Jan Shift 2) JEE Main Previous Year Paper

Q28.A small square loop of wire of side 𝑙 is placed inside a large square loop of wire of side 𝐿𝐿= 𝑙2. The loops are coplanar and their centers coincide. The value of the mutual inductance of the system is √𝑥× 10-7 H, where 𝑥= ______.

Q28.A rectangular loop of sides 12 cm and 5 cm, with its sides parallel to the 𝑥-axis and 𝑦-axis respectively moves with a velocity of 5 cm s-1 in the positive 𝑥 axis direction, in a space containing a variable magnetic field in the positive 𝑧 direction. The field has a gradient of 10-3 T cm-1 along the negative 𝑥 direction and it is decreasing with time at the rate of 10-3 T s-1 . If the resistance of the loop is 6 m𝛺, the power dissipated by the loop as heat is ______ × 10-9 W .

Q28.The magnetic flux 𝜙 (in weber) linked with a closed circuit of resistance 8 𝛺 varies with time (in seconds) as 𝜙= 5𝑡2 −36𝑡+ 1. The induced current in the circuit at 𝑡 = 2 s is _______ A.

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.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.