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

Published on: 12/10/2020

12th Standard Physics English Medium Free Online Test one mark questions 2020

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

For a transistor \(\frac{I_C}{I_E}\) = 0.96, then CE current gain is ______________.

(a)

(b)

(c)

(d)

The minimum wavelength of the X-rays produced by electrons accelerated through a potential difference of V volts is directly proportional to _____________.

(a)

\(\frac { 1 }{ \sqrt { V } } \)

(b)

\(\frac { 1 }{ V } \)

(c)

\(\sqrt { V } \)

(d)

V²

The gravitational waves were theoretically proposed by _____.

(a)

Conrad Rontgen

(b)

Marie Curie

(c)

Albert Einstein

(d)

Edward Purcell

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

(a)

75 kHz

(b)

68 kHz

(c)

80 kHz

(d)

70 kHz

The principle based on which a solar cell operates is______.

(a)

Diffusion

(b)

Recombination

(c)

Photovoltaic action

(d)

Carrier flow

In J.J. Thomson e/m experiment, electrons are accelerated through 2.6 kV enter the region of crossed electric field and magnetic field of strength 3.0 x 10⁴ Vm^-1 and 1.0 x 10^-3 T, respectively, and pass through it and undeflected, then the specific charge is _____.

(a)

1.6 × 10¹⁰ C kg^–1

(b)

1.7 × 10¹¹ Ckg^–1

(c)

1.5 × 10¹¹ Ckg^–1

(d)

1.8 × 10¹¹ Ckg^–1

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

Stars twinkle due to, ______.

(a)

reflection

(b)

total internal reflection

(c)

refraction

(d)

polarisation

The existence of E.M. waves was confirmed experimentally by __________________.

(a)

Hertz

(b)

Maxwell

(c)

Huygens

(d)

Planck

10.

Which one of the following equation is correct with respect to an ammeter?

(a)

I_gG = I_gS

(b)

(I - I_g) G = I_gS

(c)

I_gG = (I - I_g)S

(d)

I_gG = (I + I_g)S

11.

According to Joule's heating effect the law of resistance is _______________.

(a)

H ∝ R

(b)

H ∝ R²

(c)

R ∝ H²

(d)

all the above

12.

Kirchhoff's I law is a consequence of__________

(a)

law of conservation of energy

(b)

law of conservation of charges

(c)

law of conservation of currents

(d)

law of conservation of voltages

13.

A current carrying conductor is associated with _______________.

(a)

electric field

(b)

magnetic field

(c)

electro magnetic

(d)

all these

14.

The specific resistance for the insulators is in the range of________

(a)

10^-610-⁸\(\Omega m\)

(b)

10⁸-10¹⁴\(\Omega m\)

(c)

10^-8-10^-14\(\Omega m\)

(d)

10^-8-10¹⁴\(\Omega m\)

15.

5A of current flowing through a resistor for 2 minute produces 3000 j of heat. The value of the resistance is ____________.

(a)

1\(\Omega \)

(b)

2\(\Omega \)

(c)

4\(\Omega \)

(d)

5\(\Omega \)

16.

Which one of the following relation is correct?

(a)

V = \(\frac{q}{C}\)

(b)

C = q tan q

(c)

V = qC

(d)

\(\frac{V}{C}\)

17.

Fuse wire is an alloy of

(a)

37 % lead and 63 % tin

(b)

63 % lead and 37 % tin

(c)

37 % copper and 63 % tin

(d)

63 % copper and 37 % tin

18.

A potential difference is applied an the ends of a metallic wire. If the potential difference is doubled, the drift velocity ________________.

(a)

will be doubled

(b)

will be halved

(c)

will be quadrupled

(d)

will remain unchanged

19.

A metallic block has no potential difference applied across it, then the mean velocity of free electrons is _____________.

(a)

proportional to T

(b)

proportional for \(\sqrt { T } \)

(c)

finite but independent of temperature

(d)

zero

20.

The figure shows tow parallel equipotential surface A and B kept at a small distance 'r' a part from each other. A point change of Q coulomb is taken from the surface A to B. The amount of net work done will be

(a)

\(W=\frac { -1 }{ 4\pi { \varepsilon }_{ 0 }r } \frac { q }{ r } \)

(b)

\(W=\frac { 1 }{ 4\pi { \varepsilon }_{ 0 }r } \frac { q }{ r } \)

(c)

\(W=\frac { -1 }{ 4\pi { \varepsilon }_{ 0 }r } \frac { q }{ r^2 } \)

(d)

zero

21.

An electron moves in a straight line inside a charged parallel plate capacitor of uniform charge density σ. The time taken by the electron to cross the parallel plate capacitor undeflected when the plates of the capacitor are kept under constant magnetic field of induction \((\vec{B})\) is

(a)

\({ \varepsilon }_{ ° }\frac { elB }{ \sigma } \)

(b)

\({ \varepsilon }_{ ° }\frac { lB }{ \sigma {l} } \)

(c)

\({ \varepsilon }_{ ° }\frac { lB }{ {e}\sigma } \)

(d)

\({ \varepsilon }_{ ° }\frac { lB }{ \sigma } \)

22.

The flux linked with a coil at any instant t is given by \(\Phi\)_B = 10t²− 50t + 250. The induced emf at t = 3s is

(a)

−190 V

(b)

−10 V

(c)

10 V

(d)

190 V

23.

In an electromagnetic wave traveling in free space the rms value of the electric field is 3 V m⁻¹. The peak value of the magnetic field is _____.

(a)

1.414 x 10^-8 T

(b)

1.0 x 10^-8 T

(c)

2.828 x 10^-8 T

(d)

2.0 x 10^-8 T

24.

Two identical conducting balls having positive charges q₁ and q₂ are separated by a centre to centre distance r. If they are made to touch each other and then separated to the same distance, the force between them will be _____.

(a)

less than before

(b)

same as before

(c)

more than before

(d)

zero

25.

A toaster operating at 240 V has a resistance of 120 Ω. The power is ______.

(a)

400 W

(b)

2 W

(c)

480 W

(d)

240 W

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Answers Key:

Multiple Choice Question

25 x 1 = 25

\(\begin{array}{l} \beta=\frac{a}{1-\alpha} \\ \beta=\frac{0.96}{1-0.96}=24 \end{array}\)

(b)
\(\frac { 1 }{ V } \)

Albert Einstein theoretically proposed the existence of gravitational waves in the year 1915.

(a)
75 kHz

(b)
1.7 × 10¹¹ Ckg^–1

\(\frac{\mathrm{hc}}{\lambda}=\phi+\mathrm{eV} \) .....(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⋋

(a)
Hertz

10.

11.

(a)
H ∝ R

12.

(b)
law of conservation of charges

13.

(b)
magnetic field

14.

(b)
10⁸-10¹⁴\(\Omega m\)

15.

(a)
1\(\Omega \)

16.

(a)
V = \(\frac{q}{C}\)

17.

(a)
37 % lead and 63 % tin

18.

(a)
will be doubled

19.

(d)
zero

20.

(d)
zero

21.

Electric field between the plates \(= \frac{σ}{ε_0}\)
Electric force on an electron \(= e\frac{σ}{ε_0}\)
Magnetic force on an electron, F = BIl
But, \(I= \frac{e}{t}\)
∵Electron moves in a straight line. So,
E_F= M_F
\(e\frac{σ}{ε_0}=B(\frac{e}{t})l\)
\(\therefore t = ε_0\frac{lB}{σ}\)

22.

\(\phi_B =10 t^2-50 t+250 \)
\(e =\frac{-d \phi_B}{d t} \)
\(=\frac{-d}{d t}\left(10 t^2-50 t+250\right) \)
=-(20 t - 50)
=-20 t + 50
When, t = 3 s, e =-20(3) + 50 = -60 + 50
e = -10V

23.

\(B_o=\frac{E_o}{C}=\frac{\sqrt2E_{rms}}{C}\)
\(B_o=\frac{\sqrt2 \times 3}{3 \times10^8}=1.414 \times10^{-8}T\)

24.

Force ∝ charge
After the separation, the magnitude of charge will be increased. So the force will be more than before.

25.

\(P=\frac{V^2}{R}=\frac{240 \times 240}{120}=480 \ W\)