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12th Standard Physics English Medium Free Online Test 1 mark questions 2020 - Part Four

Published on: 12/10/2020

12th Standard Physics English Medium Free Online Test 1 mark questions 2020 Part Four

Download Tamil Nadu 12th Standard Physics question papers, model tests, one-mark questions, important questions, and public exam papers in PDF format. Free study materials and answer keys for TN State Board students.

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Std: 12th Standard - Physics

chapter: - Model Question paper

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Questions:

Multiple Choice Question

25 x 1 = 25

A small piece of wire bent into an L shape with an upright and horizontal portion of equal length, is placed with the horizontal portion along the axis of the concave mirror whose radius of curvature is 10 cm. If the bend is 20 cm from the pole of the mirror, then the ratio of lengths of the image of the upright and horizontal position of the wire is _____________.

(a)

1: 2

(b)

3: 1

(c)

1: 3

(d)

2: 1

Below the threshold frequency, if the intensity of radiation is increased, the emission of photoelectrons _______

(a)

increases

(b)

decreases

(c)

is zero

(d)

is a constant

What is the energy of a photon of wavelength 6000 Å?

(a)

3.3 x 10^-10 J

(b)

4.4 x 10^-19 J

(c)

3.3 x 10^-19 J

(d)

4.4 x 10^-10 J

The combination of NAND gates here under are equivalent to __________.

(a)

OR gate and NOT gate

(b)

AND gate and OR gate

(c)

AND gate and NOT gate

(d)

OR gate and AND gate

Natural uranium consists of _____________ % of U₂₃₅ and __________% of U₂₃₈

(a)

0.72, 99.28

(b)

99.28, 0.72

(c)

77.28, 72

(d)

72, 77.28

J.J. Thomson's experiment demonstrated that ______________.

(a)

cathode rays are streams of negatively charged ions

(b)

all the mass of an atom is in the nucleus

(c)

specific charge of electrons is much greater than the protons.

(d)

e/m ratio changes when different gases is placed in the discharge tube

The particle which gives mass to protons and neutrons are _____.

(a)

Higgs particle

(b)

Einstein particle

(c)

Nanoparticle

(d)

Bulk particle

The internationally accepted frequency deviation for the purpose of FM broadcasts ____________.

(a)

75 kHz

(b)

68 kHz

(c)

80 kHz

(d)

70 kHz

The specific characteristic of a common emitter amplifier is _______________.

(a)

High input resistance

(b)

Low power gain

(c)

Signal phase reversal

(d)

Low current gain

10.

M_p denotes the mass of the proton and M_n denotes mass of a neutron. A given nucleus of binding energy B, contains Z protons and N neutrons. The mass M(N, Z) of the nucleus is given by _____.(where c is the speed of light)

(a)

M (N,Z) = NM_n+ ZM_p- Bc²

(b)

M (N,Z) = NM_n+ ZM_p+ Bc²

(c)

M (N,Z) = NM_n+ ZM_p- B/c²

(d)

M (N,Z) = NM_n+ ZM_p+ B/c²

11.

Emission of electrons by the absorption of heat energy is called ______ emission.

(a)

photoelectric

(b)

field

(c)

thermionic

(d)

secondary

12.

Two point white dots are 1 mm apart on a black paper. They are viewed by eye of pupil diameter 3 mm approximately. The maximum distance at which these dots can be resolved by the eye is_____. [take wavelength of light, λ = 500 nm]

(a)

1 m

(b)

5 m

(c)

3 m

(d)

6 m

13.

Every source has its own characteristic __________ spectrum.

(a)

white

(b)

emission

(c)

scattering

(d)

absorption

14.

The angular momentum of an electron revolving in second order (n = 2) is _________________.

(a)

6.6 x 10^-34 Js

(b)

3.3 x 10^-34 Js

(c)

2.1 x 10^-34 Js

(d)

9.27 x 10^-34 Js

15.

A transformer is _____________.

(a)

converts energy

(b)

changes voltage

(c)

changes current

(d)

changes both current and voltage

16.

A square aluminum rod is 1 m long and 5 mm on edge. What must be the radius of another aluminum rod whose length is 1 m and which has the same resistance as that of square Aluminum rod?

(a)

1.4 mm

(b)

2.8 mm

(c)

4.2 mm

(d)

5.6 mm

17.

A closed system contains four charges -8.1C, 14.6C, 20.2C and -200 mC. The total charge in the system_______.

(a)

26.5 C

(b)

-173.3 C

(c)

43.1 C

(d)

243.9 C

18.

Which graph shows the variation of electric field E due to a hollow spherical conductor of radius R as a function of distance from the centre of the sphere?

(a)

(b)

(c)

(d)

19.

Two copper spheres A and B of same size are charged to same potential. A is hollow and B is solid. Which of the two holds more charge?

(a)

Solid sphere cannot hold any charge

(b)

hollow sphere cannot hold any charge

(c)

both have zero charge

(d)

both have the same charge

20.

A force of 40 N is acting between two charges in air if the space between then is filled with glass ε_r = 8. Then the force between then is __________

(a)

20 N

(b)

10 N

(c)

5 N

(d)

the same and does not change

21.

A flat dielectric disc of radius R carries an excess charge on its surface. The surface charge density is σ. The disc rotates about an axis perpendicular to its plane passing through the center with angular velocity ω. Find the magnitude of the torque on the disc if it is placed in a uniform magnetic field whose strength is B which is directed perpendicular to the axis of rotation.

(a)

\(\frac { 1 }{ 4 } \sigma \omega \pi BR\)

(b)

\(\frac { 1 }{ 2 } \sigma \omega \pi B{ R }^{ 2 }\)

(c)

\(\frac { 1 }{ 4 } \sigma \omega \pi B{ R }^{ 3 }\)

(d)

\(\frac { 1 }{ 4 } \sigma \omega \pi B{ R }^{ 4 }\)

22.

An inductor 20 mH, a capacitor 50 μF and a resistor 40Ω are connected in series across a source of emf V = 10 sin 340 t. The power loss in AC circuit is

(a)

0.76 W

(b)

0.89 W

(c)

0.46 W

(d)

0.67 W

23.

If E = E_o sin[10⁶ x -ωt] be the electric field of a plane electromagnetic wave, the value of ω is_____.

(a)

0.3 x 10⁻¹⁴ rad s⁻¹

(b)

3 x 10⁻¹⁴ rad s⁻¹

(c)

0.3 x 10¹⁴ rad s⁻¹

(d)

3 x 10¹⁴ rad s^-1

24.

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

(a)

Q remains the same, C is doubled

(b)

Q is doubled, C doubled

(c)

C remains same, Q doubled

(d)

Both Q and C remain same

25.

The temperature coefficient of resistance of a wire is 0.00125 per °C. At 20°C, its resistance is 1 Ω. The resistance of the wire will be 2 Ω at ______.

(a)

800 °C

(b)

700 °C

(c)

850 °C

(d)

820 °C

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Answers Key:

Multiple Choice Question

25 x 1 = 25

(b)
3: 1

(a)
3.3 x 10^-10 J

(d)
OR gate and AND gate

(a)
0.72, 99.28

Proton and neutron are made up of quarks. Later, it was found that Higg's particles or God particles give mass to the particles like protons, neutrons etc.

(a)
75 kHz

10.

B = ∆m x c²
∆m = \(\frac{B}{c^2}\)
N M_n + Z M_p - M(N,Z) = \(\frac{B}{c^2}\)
N (N,Z) = N M_n + ZM_p - \(\frac{B}{c^2}\)

11.

12.

λ = 500 nm = 500 x 10^-9 m
x = 3 mm = 3 x 10^-3 m
a = 1 mm = 1 x 10^-3 m
\(d=\frac{xa}{1.22 \lambda}\)
\(d=\frac{3 \times1\times10^{-6}}{1.22 \times500\times10^{-9}}\)
\(=\frac{3 \times1\times10^{-6}}{6.10 \times 10^{-7}}\)
\(d=\frac{30}{6.1}=5 m\)

13.

(b)
emission

14.

15.

(d)
changes both current and voltage

16.

(b)
2.8 mm

17.

(a)
26.5 C

18.

19.

(d)
both have the same charge

20.

21.

(d)
\(\frac { 1 }{ 4 } \sigma \omega \pi B{ R }^{ 4 }\)

22.

L = 20 x 10^-3H. C = 50 x 10^-6 F, R= 40Ω
enf V = 10 sin 340 t
\(\therefore V_0=10 \mathrm{~V}, \omega=340 \)
\(X_1=1 \omega^{\prime}=20 \times 10^3 \times 340 \)
\(=6800 \times 10^{-1}=6.8 \Omega \)
\(X_C=\frac{1}{C .} \)
\(=\frac{1}{50 \times 10^{-\alpha} \times 340}=\frac{10^{\circ}}{17000}=\frac{10^{\prime}}{17}=58.823 \Omega \)
\(Z=\sqrt{R^2+\left(X_6-X_1\right)^2} \)
\(=\sqrt{(40)^2+(58.82-6.8)^2} \)
\(=\sqrt{(40)^2+(52.02)^2} \)
\(=65.62 \Omega\)
The peak current in the circuit is,
\(I_0=\frac{V_0}{Z}=\frac{10}{65.62} \)
\(\cos 0=\frac{R}{Z}=\frac{40}{65.62} \)
\(\text{Power loss in A.C. circuit }=V_{r m} 1_{r \rightarrow \infty} \cos \phi \)
\(=\frac{1}{2} V_{\mathrm{o}} I_{\mathrm{c}} \cos \phi \)
\(=\frac{1}{2} \times 10 \times \frac{10}{65.62} \times \frac{40}{65.62}\)
\(\frac{2000}{4305.98}\)
= 0.46 W