Practice Questions

Q46.The magnetic field inside a 200 turns solenoid of radius 10 cm is 2.9 × 10−4Tesla. If the solenoid carries a current of 0.29 A , then the length of the solenoid is ________ πcm .

Q46.A positive ion A and a negative ion B has charges 6.67 × 10−19C and 9.6 × 10−10C, and masses 19.2 × 10−27 kg and 9 × 10−27 kg respectively. At an instant, the ions are separated by a certain distance r. At that instant the ratio of the magnitudes of electrostatic force to gravitational force is P × 1045 , where the value of 10 P is (Take 1 = 9 × 109Nm2C−1 and universal gravitational constant as 6.67 × 10−11Nm2 kg−2 4πε0 ) Assume that charge may not be an integral multiple of electrons.

Q46.The ratio of the power of a light source S1 to that the light source S2 is 2. S1 is emitting 2 × 1015 photons per second at 600 nm . If the wavelength of the source S2 is 300 nm , then the number of photons per second emitted by S2 is … … ×1014 . 2025 (24 Jan Shift 2) JEE Main Previous Year Paper

Q46.A time varying potential difference is applied between the plates of a parallel plate capacitor of capacitance 2.5μ F. The dielectric constant of the medium between the capacitor plates is 1 . It produces an instantaneous displacement current of 0.25 mA in the intervening space between the capacitor plates, the magnitude of the rate of change of the potential difference will be _____ Vs−1 .

Q47.Two soap bubbles of radius 2 cm and 4 cm , respectively, are in contact with each other. The radius of curvature of the common surface, in cm , is ______ . and

Q47.The coordinates of a particle with respect to origin in a given reference frame is (1, 1, 1) meters. If a force of → F = ^i −^j + ^k acts on the particle, then the magnitude of torque (with respect to origin) in z-direction is ______.

Q47. In the given circuit the sliding contact is pulled outwards such that electric current in the circuit changes at the rate of 8 A/s. At an instant when R is 12Ω, the value of the current in the circuit will be ______ A.

Q47.In a measurement, it is asked to find modulus of elasticity per unit torque applied on the system. The measured quantity has dimension of [M aLbT c]. If b = −3, the value of c is ________

Q47.The net current flowing in the given circuit is_______ A.

Q47.A square loop of sides a = 1 m is held normally in front of a point charge q = 1C. The flux of the electric 1 Nm2 field through the shaded region is , where the value of p is _____. 5 × p C ε0

Q47. A string of length L is fixed at one end and carries a mass of M at the other end. The mass makes ( π3 ) rotations per second about the vertical axis passing through end of the string as shown. The tension in the string is … … ML.

Q47.In a series LCR circuit, a resistor of 300Ω, a capacitor of 25 nF and an inductor of 100 mH are used. For maximum current in the circuit, the angular frequency of the ac source is _____ ×104 radians s−1 .

Q47.The value of current I in the electrical circuit as given below, when potential at A is equal to the potential at B, will be ____ A.

Q47.A parallel plate capacitor consisting of two circular plates of radius 10 cm is being charged by a constant current of 0.15 A . If the rate of change of potential difference between the plates is 7 × 108 V/s then the integer value of the distance between the parallel plates is ( Take, ϵ0 = 9 × 10−12 mF , π = 227 ) ________ μm . 2025 (29 Jan Shift 2) JEE Main Previous Year Paper

Q48.Two light beams fall on a transparent material block at point 1 and 2 with angle θ1 and θ2′ respectively, as shown in figure. After refraction, the beams intersect at point 3 which is exactly on the interface at other end of the block. Given : the distance between 1 and 2, d = 4√3 cm and θ1 = θ2 = cos−1 ( 2n1n2 ), where refractive index of the block n2 > refractive index of the outside medium n1 , then the thickness of the block is ________ cm.

Q48.The temperature of 1 mole of an ideal monoatomic gas is increased by 50∘C at constant pressure. The total heat added and change in internal energy are E1 and E2 , respectively. If E1 = x9 then the value of x is _____ E2

Q48.The position vectors of two 1 kg particles, (A) and (B), are given by→rA = (α1t2^i + α2t^j + α3t^k)m , respectively; →rB = (β1t^i + β2t2^j + β3t^k)m (α1 = 1 m/s2, α2 = 3nm/s, α3 = 2 m/s, β1 = 2 m/s, β2 = −1 m/s2, β3 = 4pm/s), where t is time, n and p −→ are constants. At t = 1 s, VA = →VB and velocities →VA and →VB of the particles are orthogonal to each other. At t = 1 s, the magnitude of angular momentum of particle (A) with respect to the position of particle (B) is √Lkgm2 s−1 . The value of L is _______ .

Q48.A tiny metallic rectangular sheet has length and breadth of 5 mm and 2.5 mm , respectively. Using a specially designed screw gauge which has pitch of 0.75 mm and 15 divisions in the circular scale, you are asked to find the area of the sheet. In this measurement, the maximum fractional error will be x where x is _________. 100

Q48.Two planets, A and B are orbiting a common star in circular orbits of radii RA and RB , respectively, with RB = 2RA . The planet B is 4√2 times more massive than planet A . The ratio ( LBLA ) of angular momentum (LB) of planet B to that of planet A (LA) is closest to integer ________.

Q48.The increase in pressure required to decrease the volume of a water sample by 0.2% is P × 105Nm−2 . Bulk modulus of water is 2.15 × 109Nm−2 . The value of P is … …

Q48.An air bubble of radius 1.0 mm is observed at a depth of 20 cm below the free surface of a liquid having surface tension 0.095 J/m2 and density 103 kg/m3 . The difference between pressure inside the bubble and atmospheric pressure is _____ N/m2 . (Take g = 10 m/s2 )

Q48.Two particles are located at equal distance from origin. The position vectors of those are represented by ¯A = 2^i + 3n^j + 2^k and ¯B = 2^i −2^j + 4p^k, respectively. If both the vectors are at right angle to each other, the value of n−1 is _____ .

Q48.A parallel plate capacitor of area A = 16 cm2 and separation between the plates 10 cm , is charged by a DC current. Consider a hypothetical plane surface of area A0 = 3.2 cm2 inside the capacitor and parallel to the plates. At an instant, the current through the circuit is 6A. At the same instant the displacement current through A0 is ________ mA .

Q48.An electric dipole of dipole moment 6 × 10−6Cm is placed in uniform electric field of magnitude 106 V/m . Initially, the dipole moment is parallel to electric field. The work that needs to be done on the dipole to make its dipole moment opposite to the field, will be ____ J.

Q49. A conducting bar moves on two conducting rails as shown in the figure. A constant magnetic field B exists into the page. The bar starts to move from the vertex at time t = 0 with a constant velocity. If the induced EMF is E ∝tn , then value of n is _.