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12th Standard Physics English Medium Free Online Test one mark questions with answer key 2020 - Part Two

Published on: 12/10/2020

12th Standard Physics English Medium Free Online Test one mark questions with answer key 2020 Part Two

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 rear mirror of a vehicle is cylindrical having a radius of curvature of 10 cm. The length of the arc of the curved surface is also 10 cm. If the eye of the driver is assumed to be at a large distance, from the mirror, then the field of view in radian is ____________.

(a)

0.5

(b)

(c)

(d)

The image formed by a convex mirror of a real object is larger than the object _____________.

(a)

when μ <21

(b)

when μ > 2f

(c)

for all values of μ

(d)

for no value of μ

Zno is an example of __________

(a)

Bulk solid

(b)

Nano solid

(c)

Bulk solid and Nano solid

(d)

None of the above

__________ Scanning Electron Micrograph (SEM) showing the nano structures on the surface of a leaf from a lotus plant

(a)

Parrot fish

(b)

Morpho butterfly

(c)

Lotus leaf surface

(d)

Peacock feathers

Bodies in non-inertial frames disobey ________

(a)

Newton's law

(b)

Theory of Relativity

(c)

General Relativity

(d)

Einstein's theories

The photoelectric current is due to the flow of _______

(a)

photons

(b)

protons

(c)

electrons

(d)

holes

In the photoelectric phenomenon, if the ratio of the frequency of incident radiation incident on a photosensitive surface is 1: 2: 3, the ratio of the photoelectric current is _____________.

(a)

1: 2 : 3

(b)

\(\sqrt { 1 } :\sqrt { 2 } :\sqrt { 3 } \)

(c)

1: 4 : 9

(d)

1: 1 : 1

Einstein's work on photoelectric effect gives support to _______________.

(a)

E = mc²

(b)

E=hv

(c)

hg-\(\frac{1}{2}\) mv²

(d)

E=\(\frac { h }{ \lambda } \)

Sodium and copper have work functions of 2.3eV and 4.5eV respectively, then the ratio of the wavelengths is nearest to ___________.

(a)

1: 2

(b)

4: 1

(c)

2: 1

(d)

1: 4

10.

The anode plate in an experiment on photoelectric effect is kept vertically above the emitter plate. Light source is put on. An electric field is switched on which has vertically downward direction.

(a)

The photo current will increase

(b)

The kinetic energy of the electrons will increase

(c)

The stopping potential will decrease

(d)

The transhold wavelength will increase

11.

The ground state energy of a hydrogen atom is 13.6 eV. The energy needed to ionize H₂ atom from its second excited state ______________.

(a)

1.51 eV

(b)

3.4 eV

(c)

13.6 eV

(d)

none

12.

The frequency range of 3 MHz to 30 MHz is used for ______.

(a)

Ground wave propagation

(b)

Space wave propagation

(c)

Sky wave propagation

(d)

Satellite communication

13.

The given electrical network is equivalent to ______.

(a)

AND gate

(b)

OR gate

(c)

NOR gate

(d)

NOT gate

14.

If a positive half-wave rectified voltage is fed to a load resistor, for which part of a cycle there will be current flow through the load?

(a)

0⁰–90⁰

(b)

90⁰–180⁰

(c)

0⁰–180⁰

(d)

0⁰–360⁰

15.

If the nuclear radius of ²⁷Al is 3.6 fermi, the approximate nuclear radius of ⁶⁴Cu, in femi is _____.

(a)

2:4

(b)

1.2

(c)

4.8

(d)

3.6

16.

When a metallic surface is illuminated with radiation of wavelength λ, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2λ, the stopping potential is \(\frac{V}{4}\). The threshold wavelength for the metallic surface is _____.

(a)

4λ

(b)

5λ

(c)

\(\frac{5}{2}λ\)

(d)

3λ

17.

For light incident from air on a slab of refractive index 2, the maximum possible angle of refraction is, ______.

(a)

30^o

(b)

45^o

(c)

60^o

(d)

90^o

18.

Which of the following statement on equipotential surface is wrong?

(a)

The potential difference between any two points on the surface, is zero.

(b)

The electric field is always perpendicular to the surface

(c)

Equipotential surface is always spherical.

(d)

No work is done in moving a charge along the surface

19.

What will happen if two conducting spheres are separately charged and then brought in contact?

(a)

Total charge on the two spheres is conserved

(b)

The total energy is conserved

(c)

Both charge and energy are conserved

(d)

The final potential is the mean of the original potentials.

20.

A bar magnet of length l and magnetic moment p_m is bent in the form of an arc as shown in Figure. The new magnetic dipole moment will be

(a)

p_m

(b)

\(\frac{3}{\pi} p_{m}\)

(c)

\(\frac{2}{\pi} p_{m}\)

(d)

\(\frac{1}{2} p_{m}\)

21.

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 fields is

(a)

\(\frac{Q}{2}\)

(b)

\(\frac{Q}{\sqrt3}\)

(c)

\(\frac{Q}{\sqrt2}\)

(d)

22.

When the current changes from +2A to −2A in 0.05 s, an emf of 8 V is induced in a coil. The co-efficient of self-induction of the coil is

(a)

0.2H

(b)

0.4H

(c)

0.8H

(d)

0.1H

23.

If the magnetic monopole exists, then which of the Maxwell’s equation to be modified?

(a)

\(\oint { \vec { E } .d\vec { A } } =\frac { { Q }_{ enclosed } }{ { \in }_{ 0 } } \)

(b)

\(\oint { \vec { B } .d\vec { A } } \) = 0

(c)

\(\oint { \vec { B } .d\vec { l } } ={ \mu }_{ 0 }{ i }_{ c}+{ \mu }_{ 0 }{ \in }_{ 0 }\frac { d }{ dt } \oint_s { \vec { E } .d\vec { A } } \)

(d)

\(\oint { \vec { E } .d\vec { l } } =-\frac { d }{ dt } { \Phi }_{ B }\)

24.

An electric field \(\vec { E } =10x\hat { i } \) exists in a certain region of space. Then the potential difference V = V_o – V_A, where V_o is the potential at the origin and V_A is the potential at x = 2 m is _____.

(a)

10 V

(b)

-20 V

(c)

+20 V

(d)

-10 V

25.

A piece of copper and another of germanium are cooled from room temperature to 80 K. The resistance of ______.

(a)

each of them increases

(b)

each of them decreases

(c)

copper increases and germanium decreases

(d)

copper decreases and germanium increases

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Answers Key:

Multiple Choice Question

25 x 1 = 25

(b)
1

(d)
for no value of μ

(a)
Newton's law

(d)
1: 1 : 1

(b)
E=hv

10.

(b)
The kinetic energy of the electrons will increase

11.

(a)
1.51 eV

12.

Ground wave propagation: frequency less than 2 MHz
Sky wave propagation: 3 to 30 MHz
Space wave propagation: Above 30 MHz to 400 GHz
Satellite communication: uplink communication 6 GHz band downlink communication 4 GHz band

13.

\(Y_1=\overline{A+B}, y_2=\overline{A+B}=A+B, y=\overline{A+B}\)

14.

15.

\(r \propto A^{\frac{1}{3}} \)
\(\frac{r_{\mathrm{Cu}}}{\mathrm{r}_{\mathrm{Al}}}=\frac{\mathrm{A}_{\mathrm{Cu}}^\frac{1}{3}}{\mathrm{~A}_{\mathrm{Al}}^{\frac{1}{3}}}=\frac{4}{3} \)
\(\mathrm{r}_{\mathrm{Cu}}=\frac{4}{3} \times 3.6 \mathrm{~F}=4.8 \mathrm{~F}\)

16.

\(\frac{\mathrm{hc}}{\lambda}=\phi+\mathrm{eV} \) .....(1)
\(\frac{\mathrm{hc}}{2 \lambda}=\phi+\frac{\mathrm{eV}}{4}\) .....(2)
multiply (2) eqn by 4
\(\frac{2 h c}{\lambda}=4 \phi+\mathrm{eV}\) .....(3)
subtract eqn (1) from (3), we get
\(\frac{ h c}{\lambda}=3 \phi \Rightarrow \phi = \frac{ h c}{3\lambda}\)
\(\frac{ h c}{\lambda_o}=\frac{ h c}{3\lambda}\)
⋋_o = 3⋋

17.

(a)
30^o

18.

(a)
The potential difference between any two points on the surface, is zero.

19.

(a)
Total charge on the two spheres is conserved

20.

Magnetic moment,
p'_m = ml
From figure, \(l=\frac{\pi r}{3}\)
\(\therefore r=\frac{3l}{\pi}\)
∴ New magnetic moment,
p'_m = m x r
\(=m\times \frac{3l}{\pi}=\frac{3}{\pi}ml\)
∴ p'_m = \(\frac{3}{\pi}p_m\)

21.

\(Q_{midpoint}=\frac{Q}{\sqrt{1^2+1^2}}=\frac{Q}{\sqrt2}\)

22.

\(\text {emf } e=8 \mathrm{~V} \)
\(d I=I_1-I_0=2-(-2)=4 \mathrm{~A} \)
\(\text {dt }=0.05 \mathrm{~s} \)
\(L=\frac{-e}{d I / d t}=\frac{-8}{4 / 0.05} \)
\(=\frac{-8 \times 0.05}{4}=\frac{-0.40}{4} \)
=-0.1 H
-ve sign indicates that self-induced emf always opposes the current w.r.t. time.

23.

(b)
\(\oint { \vec { B } .d\vec { A } } \) = 0

24.

\(\vec {E}\) = 10x\(\hat{i},\) when x = 2 m
\(\vec {E}\) = 10 x 2 x \(\hat{i}\) = 20\(\hat{i}\)
Since, \(E=\frac{-dV}{dx}\therefore V=+20 V\)

25.

Resistivity ∝ temperature for conductor. so, copper → decreases
Resistivity ∝\(\frac{1}{\text {temperature for semiconductor}}\)
so, germanium → increases.