Moving Charges & Magnetism PYQs Set 4 (PDF)

Set 4 of 19 · Questions 91-120 of 549

In the print window choose “Save as PDF”. The file prints without a web address or date line.

Mere Teacher · Previous Year Questions JEE Main Physics · Moving Charges & Magnetism · Set 4 (Q91-120)
Scan or visit mereteacher.com for free PYQ practice, timed CBT tests, step-by-step solutions and BroBot AI. Answers and solutions are free with a sign-up.
91. $It is found that a non-zero current element is unable to produce any magnetic field at a particular point. Then the angle between the current element and the position vector of that point with respect to the current element is$ (1) $must be 45^{\circ}$ (2) $may be 0^{\circ} or 180^{\circ}$ (3) $must be 90^{\circ}$ (4) $may be 30^{\circ} to 60^{\circ}$ 92. $A short bar magnet of magnetic moment 0.4J T^{-1} is place in a uniform magnetic field of 0.16 T. The magnet is in stable equilibrium when the potential energy is:$ (1) $-0.064 J$ (2) $zero$ (3) $- 0.082 J$ (4) $0.064$ 93. $A galvanometer of resistance 50Ω is connected to a battery of 3 V along with a resistance of 2950Ω in series shows full-scale deflection of 30 divisions. The additional series resistance required to reduce the deflection to 20 divisions is$ (1) $4440Ω$ (2) $1500Ω$ (3) $7400Ω$ (4) $2950Ω$ 94. $A galvanometer coil has a resistance of 15 ohm and gives full scale deflection for a current of 4 mA . To convert it to an ammeter of range 0 to 6 A,$ (1) $10 mΩ resistance is to be connected in parallel to the galvanometer$ (2) $10 mΩ resistance is to be connected in series with the galvanometer$ (3) $0.1Ω resistance is to be connected in parallel to the galvanometer$ (4) $0.1Ω resistance is to be connected in series with the galvanometer.$ 95. $If a velocity has both perpendicular and parallel components while moving through a magnetic field, what is the path followed by a charged particle?$ (1) $Linear$ (2) $Circular$ (3) $Helical$ (4) $Elliptical$ 96. $A charge q moves in a region where electric field and magnetic field both exist, then force on it is$ (1) $q (v \times B) .$ (2) $q E + q (v \times B)$ (3) $q E + q (B \times v)$ (4) $q B + q (E \times v)$ 97. $A proton and a deutron (q = + e, m = 2.0 u) having same kinetic energies enter a region of uniform magnetic field B, moving perpendicular to B . The ratio of the radius r_{d} of deutron path to the radius r_{p} of the proton path is:$ (1) $2 : 1$ (2) $1 : 1$ (3) $1 : 2$ (4) $1 : 2$ 98. $An electron (mass m) is accelerated through a potential difference of ' V' and then it enters in a magnetic field of induction ' B' normal to the lines. The radius of the circular path is (e = electronic charge)$ (1) $\frac{2 eV}{m}$ (2) $\frac{2 Vm}{e B ^{2}}$ (3) $\frac{2 Vm}{eB}$ (4) $\frac{2 Vm}{e ^{2} B}$ 99. $A charged particle is moving in a magnetic field of strength B perpendicular to the direction of the field. If q and m denote the charge and mass of the particle respectively, then the frequency of rotation of the particle is$ (1) $f = \frac{qB}{2 πm}$ (2) $f = \frac{qB}{2 π m ^{2}}$ (3) $f = \frac{2 π ^{2} m}{qB}$ (4) $f = \frac{2 πm}{qB}$ 100. $A galvanometer having a resistance of 9 ohm is shunted by a wire of resistance 2 ohm. If the total current is 1 amp, the part of it passing through the shunt will be$ (1) $0.2 amp$ (2) $0.8 amp$ (3) $0.25 amp$ (4) $0.5 amp$ 101. $If there is no torsion in the suspension thread, then the time period of a magnet executing SHM is$ (1) $T = \frac{1}{2 π} \frac{I}{MB}$ (2) $T = 2 π \frac{MB}{I}$ (3) $T = \frac{1}{2 π} \frac{MB}{I}$ (4) $T = 2 π \frac{I}{MB}$ 102. $The radius of the path of an electron moving at a speed of 3.2 \times 10^{7} ms^{- 1} in a magnetic field of 6 \times 10^{- 4} T perpendicular to it is (mass of electron is 9 \times 10^{- 31} kg and charge of electron is 1.6 \times 10^{- 19} C)$ (1) $22.4 cm$ (2) $13 cm$ (3) $30 cm$ (4) $39 cm$ 103. $A moving coil galvanometer has a coil with 175 turns and area 1 cm^{2} . It uses a torsion band of torsion constant 10^{- 6} N - m / rad The coil is placed in a magnetic field B parallel to its plane. The coil deflects by 1^{\circ} for a current of 1 mA . The value of B (in Tesla) is approximately:$ (1) $10^{- 4}$ (2) $10^{- 2}$ (3) $10^{- 1}$ (4) $10^{- 3}$ 104. $A thin rod of length L has magnetic moment M when magnetised. If rod is bent in a semicirculat arc what is magnetic moment in new shape?$ (1) $\frac{M}{L}$ (2) $\frac{M}{π}$ (3) $\frac{M}{2 π}$ (4) $\frac{2 M}{π}$ 105. $The magnetic moments associated with two closely wound circular coils A and B of radius r_{A} = 10 cm and r_{B} = 20 cm respectively are equal if: (Where N_{A}, I_{A} and N_{B}, I_{B} are number of turn and current of A and B respectively)$ (1) $2NAIA = NBIB$ (2) $NA = 2NB$ (3) $NAIA = 4NBIB$ (4) $4 N_{A} I_{A} = N_{B} I_{B}$ 106. $Consider a circular coil of wire carrying constant current I, forming a magnetic dipole. The magnetic flux through an infinite plane that contains the circular coil and excluding the circular coil area is given by φ_{i} . The magnetic flux through the area of the circular coil area is given by φ_{o} Which of the following option is correct?$ (1) $φ_{i} > φ_{o}$ (2) $φ_{i} < φ_{o}$ (3) $φ_{i} = - φ_{o}$ (4) $φ_{i} = φ_{o}$ 107. $The electric current in a circular coil of four turns produces a magnetic induction 32 T at its center. The coil is unwound and is rewound into a circular coil of single turn, the magnetic induction at the center of the coil by the same current will be$ (1) $8T$ (2) $4T$ (3) $2T$ (4) $16T$ 108. $A solenoid 1.5 m long and 0.4 cm in diameter possesses 10 turns per cm length. A current of 5 A falls through it. The magnetic field at the axis inside the solenoid is$ (1) $2 π \times 10^{- 3} T$ (2) $2 π \times 10^{- 5} T$ (3) $4 π \times 10^{- 2} T$ (4) $4 π \times 10^{- 3} T$ 109. $A plane electromagnetic wave of frequency 25 GHz is propagating in vacuum along the z-direction. At a particular point in space and time, the magnetic field is given by B \to= 5 \times 10^{- 8} j^T . The corresponding electric field E is (Speed of light c = 3 \times 10^{8} m s^{- 1})$ (1) $1.66\times 1 0^{- 18} i^V/m$ (2) $15 i^V / m$ (3) $- 15 i^V / m$ (4) $18 i^V / m$ 110. $A 50 cm long solenoid has winding of 400 turns. What current must pass through it to produce a magnetic field of induction 4 π \times 10^{- 3} T at the centre ?$ (1) $10.5 A$ (2) $12.5 A$ (3) $25.0 A$ (4) $20.0 A$ 111. $A magnetic needle of magnetic moment 6.7 \times 1 0^{-2} A m^{2} and moment of inertia 7.5 \times 1 0^{-6} kg m^{2} is performing simple harmonic oscillations in a magnetic field of 0.01 T. Time taken for 10 complete oscillations is:$ (1) $8.76 s$ (2) $6.65 s$ (3) $8.89 s$ (4) $6.98 s$ 112. $A circular current loop of magnetic moment M is in an arbitrary orientation in an external uniform magnetic ficld B . The work done to rotate the loop by 30^{\circ} about an axis perpendicular to its plane is$ (1) $MB2$ (2) $MB$ (3) $Zero$ (4) $3MB2$ 113. $A coil is placed perpendicular to a magnetic field of 5000 T . When the field is changed to 3000 T in 2 s, an induced emf of 22 V is produced in the coil. If the diameter of the coil is 0.02 m, then the number of turns in the coil is:$ (1) $7$ (2) $70$ (3) $35$ (4) $140$ 114. $In the product F = q (v \times B) = qv \times (B i + B j + B_{0} k) For q = 1 and v = 2 i + 4 j + 6 k and F = 4 i - 20 j + 12 k What will be the complete expression for B ? [NEET 2021]$ (1) $- 8 i - 8 j - 6 k$ (2) $- 6 i - 6 j - 8 k$ (3) $8 i + 8 j - 6 k$ (4) $6 i + 6 j - 8 k$ 115. $In an experiment, electrons are accelerated, from rest, by applying a voltage of 500 V . Calculate the radius of the path if a magnetic field 100 mT is then applied. [Charge of the electron = 1.6 \times 10^{- 19} C Mass of the electron (= 9.1 \times 10^{- 31} kg)$ (1) $7.5 \times 10^{- 3} m$ (2) $7.5 \times 10^{- 2} m$ (3) $7.5 m$ (4) $7.5 \times 10^{- 4} m$ 116. $A circular coil of wire of radius ' r' has ' n' turns and carries current ' ? . The magnetic induction ' B' at a point on the axis of the coil at a distance 3 r from its centre is$ (1) $\frac{μ _{0} nI}{16 r}$ (2) $\frac{μ _{0} nI}{32 r}$ (3) $\frac{μ _{0} nI}{4 r}$ (4) $\frac{μ _{0} nI}{8 r}$ 117. $A circular coil carrying current ' l' has radius ' R' and magnetic field at the centre is ' B'. At what distance from the centre along the axis of the same coil, the magnetic field will be \frac{B}{8} ?$ (1) $R 2$ (2) $R 3$ (3) $2 R$ (4) $3 R$ 118. $Two long parallel wires are at a distance of 1 meter. Both of them carry one ampere of current. The force of attraction per unit length between the two wires is$ (1) $5 \times 1 0^{- 8} N / m$ (2) $2 \times 1 0^{- 8} N / m$ (3) $2\times 1 0^{- 7} N/m$ (4) $1 0^{- 7} N / m$ 119. $A moving coil galvanometer has 100 turns and each turn has an area of 2.0 cm^{2} . The magnetic field produced by the magnet is 0.01 T and the deflection in the coil is 0.05 radian when a current of 10 mA is passed through it. The torsional constant of the suspension wire is x \times 10^{- 5} N - m / rad . The value of x is_____$ 120. $In a meter bridge experiment the balance point in obtained if the gaps are closed by 2 Ω and 3 Ω . A shunt of X Ω is added to 3 Ω resistor to shift the balancing point by 22.5 cm. The value of X is____$