Physics 2020 Question Paper Online Test (12th Standard)

Q1

The frequency range of 30 MHz to 400 GHz is used for :

A.Satellite communication B.Ground wave propagation C.Space wave propagation D.Sky wave propagation

Q2

In an oscillating LC circuit, the maximum charge on the capacitor is Q. The charge on the capacitor when the energy is stored equally between the electric and magnetic field is :

A.Q B.\(\frac{Q}{2}\) C.\(\frac{Q}{\sqrt{3}}\) D.\(\frac{Q}{\sqrt{2}}\)

Q3

Type of material which emits white light in LED :

A.GaInN B.SiC C.AlGaP D.GaAsP

Q4

A particle of mass m, carrying charge q is accelerated through a potential of V (Volt). When this accelerated charge comes under the influence of perpendicular magnetic field, the force acting on it is :

A.\(\sqrt{\frac{2q^3BV}{m^3}}\) B.\(\sqrt{\frac{2q^3BV}{m}}\) C.\(\sqrt{\frac{q^3B^2V}{2m}}\) D.\(\sqrt{\frac{2q^3B^2V}{m}}\)

Q5

Charging current for a capacitor is 0.2 A, find the displacement current.

A.zero B.0.2 A C.0.4 A D.0.1 A

Q6

In Bohr Atom Model when the principal quantum number (n) increases the velocity of electron :

A.increases and then decreases B.increases C.decreases D.remains constant

Q7

In the given diagram a point charge +q is placed at the origin O. Work done in taking another point charge −Q from point A to point B is :

Charge +q at origin O, point A (0, a) on y-axis and point B (a, 0) on x-axis joined by a line

A.\(\frac{qQ}{4\pi\epsilon_0 a^2}\left(\frac{a}{\sqrt{2}}\right)\) B.Zero C.\(\left[\frac{-qQ}{4\pi\epsilon_0}\frac{1}{a^2}\right]\sqrt{2}a\) D.\(\left[\frac{qQ}{4\pi\epsilon_0}\frac{1}{a^2}\right]\sqrt{2}a\)

Q8

The nucleus is approximately spherical in shape. Then the surface area of nucleus having mass number A varies as :

A.\(A^{5/3}\) B.\(A^{2/3}\) C.\(A^{4/3}\) D.\(A^{1/3}\)

Q9

Two light waves from slit \(S_1\) and \(S_2\) on reaching points P and Q on a screen in Young's double slit experiment have a path difference zero and \(\frac{\lambda}{4}\) respectively. The ratio of light intensities at P and Q will be :

A.4 : 1 B.3 : 2 C.\(\sqrt{2}\) : 1 D.2 : 1

Q10

The radius of curvature of curved surface at a thin planoconvex lens is 10 cm and the refractive index is 1.5. If the plane surface is silvered then the focal length will be :

A.20 cm B.5 cm C.10 cm D.15 cm

Q11

The given electrical network is equivalent to :

Two NAND gates with inputs tied, fed by A and B, whose outputs go to a third NAND gate giving Y

A.NAND gate B.OR gate C.NOT gate D.Ex-OR gate

Q12

Magnetic field at any point at a distance R due to a long straight conductor carrying current varies as :

A.\(R^2\) B.R C.\(\frac{1}{R^2}\) D.\(\frac{1}{R}\)

Q13

If voltage applied on a capacitor is increased from V to 2 V, choose the correct conclusion.

A.Both Q and C remain the same B.Q remains the same, C is doubled C.Q is doubled, C is doubled D.C remains the same, Q is doubled

Q14

A light of wavelength 500 nm is incident on a sensitive plate of photoelectric work function 1.235 eV. The kinetic energy of the photo electrons emitted is : (Take \(h=6.6\times10^{-34}\) Js)

A.1.16 eV B.0.58 eV C.2.48 eV D.1.24 eV

Q15

The current in the circuit is :

15 V cell connected across three 15 ohm resistors in parallel

A.4 A B.1 A C.2 A D.3 A

12th Standard Physics March 2020: Online Practice Test

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