Practice Questions

Q26.First, a set of n equal resistors of 10 Ω each are connected in series to a battery of E.M.F. 20 V and internal resistance 10 Ω. A current I is observed to flow. Then, the n resistors are connected in parallel to the same battery. It is observed that the current is increased 20 times, then the value of n is ___________.

Q26.In an electrical circuit, a battery is connected to pass 20 C of charge through it in a certain given time. The potential difference between two plates of the battery is maintained at 15 V . The workdone by the battery is _______ J

Q26.For the circuit shown, the value of current at time t = 3. 2 s will be ______ A . JEE Main 2021 (27 Jul Shift 2) JEE Main Previous Year Paper [Voltage distribution V(t) is shown by Fig. (1) and the circuit is shown in Fig. (2)]

Q26.The electric field in a region is given by E = 5 E0ˆi + 5 E0ˆj field through a rectangular surface, area 0. 4 m2 parallel to the Y −Z plane is _______ N m2 C−1 .

Q26.A light beam of wavelength 500 nm is incident on a metal having work function of 1. 25 eV , placed in a magnetic field of intensity B. The electrons emitted perpendicular to the magnetic field B, with maximum kinetic energy are bent into a circular arc of radius 30 cm. The value of B is ________ ×10−7 T. Given hc = 20 × 10−26 J m, the mass of the electron = 9 × 10−31 kg. JEE Main 2021 (25 Jul Shift 2) JEE Main Previous Year Paper

Q26.A point charge of +12 μC is at a distance 6 cm vertically above the centre of a square of side 12 cm as shown in figure. The magnitude of the electric flux through the square will be _______ ×103 N m2 C−1. JEE Main 2021 (24 Feb Shift 2) JEE Main Previous Year Paper

Q26.A sinusoidal voltage of peak value 250 V is applied to a series LCR circuit, in which R = 8 Ω, L = 24 mH and C = 60 μF. The value of power dissipated at resonant condition is x kW . The value of x to the nearest integer is _______.

Q26.Four identical rectangular plates with length, l = 2 cm and breadth, b = 32 cm are arranged as shown in figure. The equivalent capacitance between A and C is xε0d . The value of x is _______. (Round off to the Nearest Integer)

Q26.A uniform heating wire of resistance 36 Ω is connected across a potential difference of 240 V . The wire is then cut into half and a potential difference of 240 V is applied across each half separately. The ratio of power dissipation in first case to the total power dissipation in the second case would be 1: 𝑥, where 𝑥 is -1

Q26.A coil in the shape of an equilateral triangle of side 10 cm lies in a vertical plane between the pole pieces of permanent magnet producing a horizontal magnetic field 20 mT. The torque acting on the coil when a current of 0. 2 A is passed through it and its plane becomes parallel to the magnetic field will be √x × 10−5 Nm . The value of x is

Q26.In 5 minutes , a body cools from 75 °C to 65 °C at room temperature of 25 °C. The temperature of body at the end of next 5 minutes is ∘C.

Q26.A series LCR circuit of R = 5 Ω, L = 20 mH and C = 0. 5 μF is connected across an AC supply of 250 V , having variable frequency. The power dissipated at resonance condition is ________ ×102 W.

Q27.The frequency of a car horn encountered a change from 400 Hz to 500 Hz . When the car approaches a vertical wall. If the speed of sound is 330 m s−1 . Then the speed of car is ___ km h−1 .

Q27.A cylindrical wire of radius 0. 5 mm and conductivity 5 × 107 S m−1 is subjected to an electric field of 10 mV m−1. The expected value of current in the wire will be x3π mA. The value of x is _________.

Q27.In Bohr's atomic model, the electron is assumed to revolve in a circular orbit of radius 0. 5 A. If the speed of electron is 2. 2 × 106 m s−1. Then the current associated with the electron will be__________ ×10−2 mA. [Take π as 22 7 ]

Q27.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 ε0 = 8. 85 × 10−12 F m−1 . The value of x to the nearest integer is ______.

Q27.The voltage drop across 15 Ω resistance in the given figure will be _______ V.

Q27.An electromagnetic wave of frequency 5GHz, is travelling in a medium whose relative electric permittivity and relative magnetic permeability both are 2 . Its velocity in this medium is _______ × 107 m s-1.

Q27.Consider a 72 cm long wire AB as shown in the figure. The galvanometer jockey is placed at P on AB at a distance x cm from A . The galvanometer shows zero deflection. JEE Main 2021 (18 Mar Shift 2) JEE Main Previous Year Paper The value of x, to the nearest integer, is

Q27.An AC circuit has an inductor and a resistor of resistance R in series, such that XL = 3R. Now, a capacitor is added in series such that XC = 2R. the ratio of the new power factor with the old power factor of the circuit is √5 : x. The value of x is

Q27.A 2μF capacitor C1 is first charged to a potential difference of 10 V using a battery. Then the battery is removed and the capacitor is connected to an uncharged capacitor C2 of 8μF. The charge in C2 on equilibrium condition is μC. (Round off to the Nearest Integer)

Q27.Two short magnetic dipoles m1 and m2 each having magnetic moment of 1 A m2 are placed at point O and P respectively. The distance between OP is 1 m . The torque experienced by the magnetic dipole m2 due to the presence of m1 is ________ × 10−7N m

Q27.The value of aluminium susceptibility is 2 . 2 × 10-5. The percentage increase in the magnetic field if space 𝑥 within a current carrying toroid is filled with aluminium is 104. Then the value of 𝑥 is

Q27.Cross-section view of a prism is the equilateral triangle 𝐴𝐵𝐶 shown in the figure. The minimum deviation is observed using this prism when the angle of incidence is equal to the prism angle. The time taken by light to travel from 𝑃 (midpoint of 𝐵𝐶) to 𝐴 is ___________ × 10-10 s . (Given, speed of light in vacuum √3 = 3 × 108 m s-1 and cos30° = ) 2

Q27.Two small spheres each of mass 10 mg are suspended from a point by threads 0. 5 m long. They are equally charged and repel each other to a distance of 0. 20 m. The charge on each of the sphere is 21a × 10−8 C. The value of a will be ___.[Given g = 10 m s−2 ]