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

Published on: 12/10/2020

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

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

The radius of curvature of a concave mirror is 40 cm and the size of the image is twice as that of an object, then the object distance is ____________.

(a)

60 cm

(b)

20 cm

(c)

40 cm

(d)

30 cm

A ray of light is incident normally on a lane mirror. The angle of reflection will be _____________.

(a)

0°

(b)

90°

(c)

will not be reflected

(d)

None of these

How many AND gates are required to form NAND gate?

(a)

(b)

(c)

(d)

Messages cannot be transmitted over long distances in _________ transmission.

(a)

(b)

(c)

(d)

PCM

Einstein's photoelectric equation is an equation of a _______

(a)

circle

(b)

sphere

(c)

straight line

(d)

ellipse

For long distance, shortwave radio broadcasting __________ wave is used.

(a)

ground

(b)

ionospheric

(c)

sky

(d)

direct

For a transistor, in a common base configuration the alternating current gain is given by ______________.

(a)

\({ \left[ \frac { \triangle { I }_{ C } }{ \triangle { I }_{ B } } \right] }_{ { V }_{ c }=constant }\)

(b)

\({ \left[ \frac { \triangle { I }_{ B } }{ \triangle { I }_{ C } } \right] }_{ { V }_{ c }=constant }\)

(c)

\({ \left[ \frac { \triangle { I }_{ C } }{ \triangle { I }_{ E } } \right] }_{ { V }_{ c }=constant }\)

(d)

\({ \left[ \frac { \triangle { I }_{ E } }{ \triangle { I }_{ C } } \right] }_{ { V }_{ c }=constant }\)

The photo current in an experiment on photoelectric effect increases if ____________.

(a)

the intensity of the source is increased

(b)

the exposure time is increased

(c)

the intensity of the source is decreased

(d)

the exposure time is decreased

The wave associated with a moving particle of mass 3 x 10^–6 g has the same wavelength as an electron moving with a velocity 6 x 10⁶ ms^-1. The velocity of the particle is _____.

(a)

1.82 x 10^-18ms^-1

(b)

9 x 10^-2ms^-1

(c)

3 x 10^-31ms^-1

(d)

1.82 x 10^-15ms^-1

10.

An object is placed in front of a convex mirror of focal length off and the maximum and minimum distance of an object from the mirror such that the image formed is real and magnified.

(a)

2f and c

(b)

c and \(\infty\)

(c)

f and O

(d)

None of these

11.

The rays used in weather forecasting is ___________.

(a)

I-R rays

(b)

U-V rays

(c)

X - rays

(d)

μ-Waves

12.

A galvanometer can be converted into a voltmeter by connecting _________________.

(a)

a low resistance in parallel to it

(b)

a high resistance in parallel to it

(c)

a low resistance in series with it

(d)

a high resistance in series with it

13.

When the number of turns (n) in a galvanometer is doubled, current sensitivity __________________.

(a)

remains constant

(b)

decreases twice

(c)

increases twice

(d)

increases four times

14.

Quality factor = ?

(a)

\(\frac{output \ power}{input \ power}\)

(b)

\(\frac{output \ current}{input \ current}\)

(c)

\(\frac{voltage \ across \ L (or) \ C}{applied \ voltage}\)

(d)

\(\frac{random \ frequency}{resonant \ frequency}\)

15.

An electron of mass 0.90 x 10^-30kg under the action of a magnetic field moves in a circle of 2cm radius at a speed of 3 x 10⁶ m/s if a proton of mass 1.8 x 10^-27 kg was to move in a circle of the same radius in the same magnetic field, then its speed will be _______________.

(a)

3.0 x 10⁶ m/s

(b)

1.5 x 10³ m/s

(c)

6.0 x 10⁴ m/s

(d)

cannot be estimated from the same data

16.

Calculate the mobility of a free electron in an electric field of 10⁺²N/C.

(a)

10^-4m²V^-1s^-1

(b)

10^-5m²V^-1s^-1

(c)

10^-3m²V^-1s^-1

(d)

10⁵m²V^-1s^-1

17.

An ideal cell is connected to a capacitor through a voltmeter. The reading V of the voltmeter is plotted against time. Which of the following best represents the resulting curve?

(a)

(b)

(c)

(d)

18.

Four resistances are connected to a 5V battery of negligible internal resistance as shown what is the potential across \(2\Omega \)?

(a)

0.5 V

(b)

1:5 V

(c)

1.0 V

(d)

1.0 V

19.

Electrostatics deals with the _________

(a)

charges in motion

(b)

static electric charges

(c)

charges through conductors

(d)

accelerated charges

20.

What physical quantities may X and Y represent? [Y represents the first mentioned quantity].

(a)

K.E - velocity of a particle

(b)

pressure - temperature of a given gas (constant volume)

(c)

capacitance - charge to give a constant potential

(d)

potential - capacitance to give a constant charge

21.

A positively charged body 'A' has been brought near a brass cylinder 'B' mounted on a glass stand as shown in the figure. The potential of 'B' will be

(a)

zero

(b)

Negative

(c)

positive

(d)

Infinite

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.

In a series resonant RLC circuit, the voltage across 100 Ω resistor is 40 V. The resonant frequency ω is 250 rad/s. If the value of C is 4 µF, then the voltage across L is

(a)

600 V

(b)

4000 V

(c)

400 V

(d)

1 V

24.

Rank the electrostatic potential energies for the given system of charges in increasing order

(a)

1 = 4 < 2 < 3

(b)

2 = 4 < 3 < 1

(c)

2 = 3 < 1 < 4

(d)

3 < 1 < 2 < 4

25.

In India electricity is supplied for domestic use at 220 V. It is supplied at 110 V in USA. If the resistance of a 60 W bulb for use in India is R, the resistance of a 60 W bulb for use in USA will be ______.

(a)

(b)

(c)

\(\frac{R}{4}\)

(d)

\(\frac{R}{2}\)

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Answers Key:

Multiple Choice Question

25 x 1 = 25

(d)
30 cm

(a)
0°

(a)
1

(b)
ionospheric

(a)
the intensity of the source is increased

\(\lambda_{\mathrm{i}} \frac{1}{\mathrm{mv}} \)
\(\frac{\lambda_p}{\lambda_e} =\frac{m_e v_e}{m_P v_P} \)
\(1 =\frac{9.1 \times 10^{-31} \times 6 \times 10^6}{3 \times 10^{-9} \times v_p} \)
\(\mathrm{v}_{\mathrm{p}} =9.1 \times 10^{-16} \times 2 \)
\(\mathrm{v}_{\mathrm{p}} =18.2 \times 10^{-16} \)
\(\mathrm{v}_{\mathrm{p}} =1.82 \times 10^{-15} \mathrm{~m} \mathrm{~s}^{-1}\)

10.

Convex Mirror is diverging in nature and for all positions of objects, convex mirror forms virtual and erect image.

11.

(a)
I-R rays

12.

(d)
a high resistance in series with it

13.

14.

15.

(b)
1.5 x 10³ m/s

16.

(b)
10^-5m²V^-1s^-1

17.

18.

19.

(b)
static electric charges

20.

(d)
potential - capacitance to give a constant charge

21.

22.

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

23.

\(\omega=250 \mathrm{rad} / \mathrm{s}, C=4 \times 10^{-} \mathrm{F} \)
\(R=100 \Omega, \quad \mathrm{V}_{\mathrm{R}}=40 \mathrm{~V} \)
\(\therefore I_{\mathrm{R}}=\frac{V_R}{100}=\frac{40}{100}=0.4 \mathrm{~A} \)
\(\omega=\frac{1}{\sqrt{L C}} \)
\(\omega^2=\frac{1}{L C} \)
\((250)^2=\frac{1}{L \times 4 \times 10^{-6}} \)
\(L=\frac{1}{4 \times(250)^2 \times 10^{-6}} \)
\(=\frac{1}{4 \times 250 \times 250 \times 10^{-6}} \)
\(=\frac{1}{1000 \times 10^{-6} \times 250} \)
\(=\frac{10^3}{250}=\frac{1000}{250}=4 \mathrm{H}\)
Voltage acnoss L, V_t= IX_L
V_L= l x L x ω
= 0.4 x 4 x 250
0.4 x 1000 = 400 V

24.

\(U=\frac{1}{4\piε_0}\frac{q_1q_2}{r_{12}}\)
\(i) U=\frac{1}{4\piε_0}\frac{Q(-Q)}{r}=\frac{1}{4\piε_0}[\frac{-Q^2}{r}]\)
\(ii) U=\frac{1}{4\piε_0}\frac{(-Q)(-Q)}{r}=\frac{1}{4\piε_0}[\frac{Q^2}{r}]\)
\(iii) U=\frac{1}{4\piε_0}\frac{Q(2Q)}{r}=\frac{1}{4\piε_0}[\frac{2Q^2}{r}]\)
\(iv) U=\frac{1}{4\piε_0}\frac{Q(-2Q)}{2r}=\frac{1}{4\piε_0}[\frac{-Q^2}{r}]\)
From the values, 1 = 4 < 2 < 3

25.

\(\mathrm{V}_1 =220 \mathrm{~V}, \quad \mathrm{P}_1=60 \mathrm{~W} \)
\(\mathrm{~V}_{\mathrm{U}} =110 \mathrm{~V}, \mathrm{P}_{\mathrm{U}}=60 \mathrm{~W} \)
\(P =\frac{V^2}{R} \Rightarrow R=\frac{V^2}{P} \)
\(\therefore R_l =\frac{V_I^2}{P_l} \text { Similarly, } \quad \mathrm{R}_U=\frac{V_U^2}{P_U} \)
\(R_l =\frac{220 \times 220}{60} \quad \mathrm{R}_{\mathrm{U}}=\frac{110 \times 110}{60} \)
\(R_I =\frac{48400}{60} \quad R_U=\frac{12100}{60} \)
\(\frac{R_U}{R_l} =\frac{12100}{60} \times \frac{60}{48400}=\frac{1}{4} \)
\(R_U =\frac{R_l}{4}=\frac{R}{4}\)