Practice Questions

Q29.The circuit contains two diodes each with a forward resistance of 50 Ω and with infinite reverse resistance. If the battery voltage is 6 V , the current through the 120 Ω resistance is _______ mA

Q29.White light is passed through a double slit and interference is observed on a screen 1. 5 m away. The separation between the slits is 0. 3 mm . The first violet and red fringes are formed 2. 0 mm and 3. 5 mm away from the central white fringes. The difference in wavelengths of red and violet light is (in nm).

Q29.An electromagnetic wave of frequency 3 GHz enters a dielectric medium of relative electric permittivity 2. 25 from vacuum. The wavelength of this wave in that medium will be _________ ×10−2 cm.

Q29.A source of light is placed in front of a screen. The intensity of light on the screen is I . Two Polaroids P1 and P2 are so placed in between the source of light and screen that the intensity of light on the screen is I2 . Then the P2 , should be rotated by an angle of (degrees) so that the intensity of light on the screen becomes 3I8 .

Q29.A ray of light passing through a prism (μ incidence is double the angle of refraction within the prism. Then, the angle of prism is (in degrees).

Q29.A transistor is connected in common emitter circuit configuration, the collector supply voltage is 10 V and the voltage drop across a resistor of 1000 Ω in the collector circuit is 0. 6 V. If the current gain factor (β) is 24, then the base current is ____ μA . (Round off to the Nearest Integer)

Q29.In a semiconductor, the number density of intrinsic charge carriers at 27°C is 1. 5 × 1016 m−3 . If the semiconductor is doped with an impurity atom, the hole density increases to 4. 5 × 1022 m−3 . The electron density in the doped semiconductor is _______ ×109 m−3

Q29.An inductor of 10 mH is connected to a 20 V battery through a resistor of 10 kΩ and a switch. After a long time, when maximum current is set up in the circuit, the current is switched off. The current in the circuit after 𝑥 1 μs is mA. Then 𝑥 is equal to ______ . (Take 𝑒-1 = 0 . 37) 100

Q29.The electric field in an electromagnetic wave is given by E = (50 N C−1) sin ω(t −xc ) The energy contained in a cylinder of volume V is 5. 5 × 10−12 J. The value of V is _______ cm3. (given ϵ0 = 8. 8 × 10−12C2 N−1 m−2 )

Q29.In connection with the circuit drawn below, the value of current flowing through 2 kΩ resistor is______ × 10-4 A .

Q29.The voltage across the 10 Ω resistor in the given circuit is x volt. The value of x to the nearest integer is _____.

Q29.The image of an object placed in air formed by a convex refracting surface is at a distance of 10 m behind the surface. The image is real and is at 2rd of the distance of the object from the surface. The wavelength of light 3 inside the surface is 2 times the wavelength in air. The radius of the curved surface is x m , the value of x 3 13 is ______ .

Q29.A current of 6 A enters one corner P of an equilateral triangle PQR having 3 wires of resistance 2 Ω each and leaves by the corner R. The currents i1 in ampere is

Q30.A TV transmission tower antenna is at a height of 20 m. Suppose that the receiving antenna is at. (i) ground level (ii) a height of 5 m. The increase in antenna range in case (ii) relative to case (i) is n%. The value of n, to the nearest integer, is.

Q30.If the highest frequency modulating a carrier is 5 kHz, then the number of AM broadcast stations accommodated in a 90 kHz bandwidth are

Q30.For VHF signal broadcasting, _______ km2 of maximum service area will be covered by an antenna tower of height 30 m, if the receiving antenna is placed at ground. Let radius of the earth be 6400 km. (Round off to the Nearest Integer) (Take π as 3. 14 )

Q30.The same size images are formed by a convex lens when the object is placed at 20 cm or at 10 cm from the lens. The focal length of convex lens is

Q30.Student 𝐴 and student 𝐵 used two screw gauges of equal pitch and 100 equal circular divisions to measure the radius of a given wire. The actual value of the radius of the wire is 0 . 322 cm. The absolute value of the difference between the final circular scale readings observed by the students 𝐴 and 𝐵 is _______. [Figure shows position of reference 𝑂 when jaws of screw gauge are closed] Given pitch = 0 . 1 cm.

Q30.In a given circuit diagram, a 5 V zener diode along with a series resistance is connected across a 50 V power supply. The minimum value of the resistance required, if the maximum zener current is 90 mA will be Ω.

Q30.For the given circuit, the power across zener diode is _____ mW .

Q30.The amplitude of upper and lower side bands of AM wave where a carrier signal with frequency 11. 21 MHz, peak voltage 15 V is amplitude modulated by a 7. 7 kHz sine wave of 5 V amplitude are 10a V and 10b V respectively. Then the value of a is_____. b JEE Main 2021 (27 Jul Shift 1) JEE Main Previous Year Paper

Q30.If the sum of the heights of transmitting and receiving antennas in the line of sight of communication is fixed at 160 m, then the maximum range of LOS communication is _______ km (Take radius of Earth = 6400 km)

Q30.The wavelength of an X-ray beam is 10 Å . The mass of a fictitious particle having the same energy as that of the X-ray photons is x h kg. The value of x is ___ . ( h =Planck's constant) 3

Q30.A signal of 0. 1 kW is transmitted in a cable. The attenuation of cable is −5 dB per km and cable length is 20 km. The power received at the receiver is 10−x W. The value of x is _________. [Gain in dB = 10 log10( POPi )]

Q30.An npn transistor operates as a common emitter amplifier with a power gain of 106. The input circuit resistance is 100 Ω and the output load resistance is 10 kΩ. The common emitter current gain β will be (Round off to the Nearest Integer)