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TN 12th Computer Applications மின்னணு தரவு பரிமாற்றம் Sample Question Papers Study Material - QB365 Set A

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TN 12th Computer Applications மின் - வணிக பாதுகாப்பு அமைப்புகள் Sample Question Papers Study Material - QB365 Set A

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TN 12th Computer Applications மின்னணு செலுத்தல் முறைகள் Sample Question Papers Study Material - QB365 Set A

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TN 12th Computer Applications மின் - வணிகம் Sample Question Papers Study Material - QB365 Set A

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

Published on: 12/10/2020

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

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

An object 5 cm tall is placed 1m from the concave spherical mirror which has a radius of curvature of 20 cm. The size of the image is _____________.

(a)

0.11 cm

(b)

0.50 cm

(c)

0.55 cm

(d)

0.60 cm

In an experiment of finding the focal length of a concave mirror, a graph is drawn between the magnitudes of u and V. the graph looks like _____________.

(a)

(b)

(c)

(d)

A plane mirror produces a magnification of ____________.

(a)

-1

(b)

+ 1

(c)

Zero

(d)

Between 0 and + ∞

The wavelength of de-Broglie waves doesn't depend on ________

(a)

mass

(b)

velocity

(c)

momentum

(d)

change

Force is the rate of change of ________

(a)

mass

(b)

acceleration

(c)

momentum

(d)

velocity

______ are used to study virus and bacteria.

(a)

Lenses

(b)

Mirrors

(c)

Electron microscope

(d)

Telescopes

The anode of a simple photo emissive cell is _______

(a)

glass tube

(b)

quartz crystal

(c)

platinum wire

(d)

iron rod

A pure semiconductor behaves slightly as a conductor of _______________.

(a)

low temperature

(b)

high temperature

(c)

room temperature

(d)

zero degree

The minimum potential given to the anode for which the photoelectric current becomes zero is called _______ potential.

(a)

cut-off

(b)

threshold

(c)

saturation

(d)

active

10.

Gases begin to conduct electricity at low pressure because ______________.

(a)

at low pressure gases turn to plasma

(b)

colliding electrons can acquire higher K.E due to increased mean free path leading to ionisation of atoms

(c)

atoms breakup into electrons and protons

(d)

the electrons in atoms can move freely at low pressure

11.

When the intensity of a light source is increased?

(a)

the number of photons emitted by the source in unit time increases

(b)

more energetic photons are emitted

(c)

faster photons are emitted

(d)

total energy of the photons emitted per unit time decreases.

12.

Cathode rays are nothing but ____________

(a)

electrons

(b)

protons

(c)

neutrons

(d)

hydrogen atoms

13.

When hydrogen atom is in its first excited level, its radius is __________ of the Bohr radius.

(a)

twice

(b)

same

(c)

half

(d)

four times

14.

The electric potential of an electron is given by \(V={ V }_{ 0 } \ In\left( \frac { r }{ { r }_{ 0 } } \right) \), where r₀ is a constant. If Bohr atom model is valid, then variation of radius of n^th orbit r_n with the principal quantum number n is _____.

(a)

\({ r }_{ n }∝ \frac { 1 }{ n } \)

(b)

\({ r }_{ n }∝ n\)

(c)

\({ r }_{ n }∝\frac { 1 }{ { n }^{ 2 } } \)

(d)

\({ r }_{ n }∝ { n }^{ 2 }\)

15.

________ radiations are used to study atomic structure.

(a)

(b)

(c)

X-rays

(d)

Gamma

16.

Radio frequency waves are produced by ______.

(a)

radioactive nuclei

(b)

radioactive nuclear reactions

(c)

accelerated charges

(d)

radio - carbon

17.

The relation between velocity of light, permeability and permittivity of free space in________.

(a)

\({ C }^{ 2 }=\frac { 1 }{ { \mu }_{ 0 }{ \varepsilon }_{ 0 } } \)

(b)

\(C=\frac { 1 }{ { \mu }_{ 0 }{ \varepsilon }_{ 0 } } \)

(c)

\({ \mu }_{ 0 }={ \varepsilon }_{ 0 }c\)

(d)

\({ \varepsilon }_{ 0 }={ \mu }_{ 0 }c\)

18.

An α-particle enters a magnetic field of 1T with a velocity 10⁶ m/s in a direction perpendicular to the field. The force on α-particle is _____________________.

(a)

1.6 x 10^-13N

(b)

6.4 x 10^-13N

(c)

4.8 x 10^-13N

(d)

3.2 x 10^-13N

19.

The temperature coefficient of resistance is positive__________.

(a)

for metals

(b)

for insulators

(c)

(a) and (b)

(d)

all the above

20.

In a transformer, eddy current loss is minimized by using ____________.

(a)

laminated core made of muemetal

(b)

laminated core made of stelloy

(c)

shell type core

(d)

thick copper wire

21.

Two charged bodies of charges +q, -3q are brought in contact and separated. The charges prossed by each body after separation.

(a)

-q,-q

(b)

+q,-2q

(c)

-q, +3q

(d)

q, q

22.

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)

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

23.

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

24.

The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 Ω is ______.

(a)

0.2 Ω

(b)

0.5 Ω

(c)

0.8 Ω

(d)

1.0 Ω

25.

A carbon resistor of (47 ± 4.7 ) k Ω to be marked with rings of different colours for its identification. The colour code sequence will be ______.

(a)

Yellow – Green – Violet – Gold

(b)

Yellow – Violet – Orange – Silver

(c)

Violet – Yellow – Orange – Silver

(d)

Green – Orange – Violet - Gold

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Answers Key:

Multiple Choice Question

25 x 1 = 25

(b)
+ 1

(d)
change

(a)
cut-off

10.

(b)
colliding electrons can acquire higher K.E due to increased mean free path leading to ionisation of atoms

11.

(a)
the number of photons emitted by the source in unit time increases

12.

(a)
electrons

13.

(d)
four times

14.

Electric potential in n^th orbit
\(\mathrm{V} =\mathrm{V}_0 \ln \left(\frac{\mathrm{r}_{\mathrm{n}}}{\mathrm{r}_0}\right) \)
\(=\mathrm{V}_0\left(\ln \mathrm{r}_{\mathrm{n}}-\ln \mathrm{r}_0\right) \)
\(=\mathrm{V}_0 \ln \mathrm{r}_{\mathrm{n}}-\mathrm{V}_0 \ln \mathrm{r}_0\)
\(\left|\mathrm{F}_\epsilon\right|=\mathrm{e} \frac{\mathrm{dv}}{\mathrm{dr}} =\mathrm{e} \frac{\mathrm{d}}{\mathrm{dr}}\left(\mathrm{V}_b / n \mathrm{r}_B-\mathrm{V}_0 / m \mathrm{r}_0\right) \)
\(=\mathrm{c}\left(\frac{\mathrm{V}_0}{\mathrm{r}_n}-0\right)=\frac{\mathrm{eV}}{\mathrm{r}_{\mathrm{n}}} \)
Centripetal force = coulomb force
\(\frac{m v^2}{r_n}=\mathrm{c} \frac{V_0}{r_n} \Rightarrow v=\sqrt{\frac{e V_0}{m}}=\text { constant }\)
Angular momentum,
\(\mathrm{mvr}_n=\frac{\mathrm{nh}}{2 \pi}\)
\(\mathrm{m}, \mathrm{v}, \mathrm{h}, 2 \pi\) are constants
hence, r_n ∝ n

15.

(a)
UV

16.

17.

(a)
\({ C }^{ 2 }=\frac { 1 }{ { \mu }_{ 0 }{ \varepsilon }_{ 0 } } \)

18.

(d)
3.2 x 10^-13N

19.

20.

(b)
laminated core made of stelloy

21.

(a)
-q,-q

22.

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

23.

If voltage is increased from V to 2 V
Then Q₁ = CV
Q₂ = C(2 V) = 2 CV
∴ Q is doubled and C remains same

24.

I = 0.2 A, R = 10 Ω, E = 2.1 V
\(I=\frac{ɛ}{R+r}\)
\(0.2=\frac{2.1}{10+r}\)
0.2 x (10 + r) = 2.1
2 + 0.2 r = 2.1
0.2 r = 2.1 - 2 = 0.1
Internal resistance, \(r=\frac{0.1}{0.2}=\frac{1}{2}\)
r = 0.5 Ω

25.

Yellow - 4
Violet - 7
Orange - 10³
Silver - Tolerance - 10%