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.

Questions:

Multiple Choice Question

49 x 1 = 49

The spectrum obtained from the photosphere of the sun is of ________ type.

(a)

band spectra

(b)

line spectra

(c)

continuous emission spectra

(d)

non-linear spectra

If white light is passed through iodine vapour, ________ are obtained.

(a)

continuous absorption spectra

(b)

continuous emission spectra

(c)

band absorption spectra

(d)

emission spectra

A pure green glass plate when, placed in the path of white light, absorbs________.

(a)

everything

(b)

everything except green

(c)

nothing

(d)

only red

The absorption spectra are characteristic of the __________.

(a)

source

(b)

absorbing substance

(c)

time of travel from source to screen

(d)

spectrometer used to study the spectrum

Carbon are produces ________ spectrum.

(a)

characteristic

(b)

line

(c)

band

(d)

continuous

Continuous spectrum depends only on the _________ of the source.

(a)

characteristic

(b)

temperature

(c)

density

(d)

volume

______ are used in weather forecasting.

(a)

IR photographs

(b)

Microwaves

(c)

Radiowaves

(d)

Visible light

The speed of electromagnetic waves in free space is ______ m/s

(a)

3 x 10^-18

(b)

6.2 x 10⁵

(c)

3 x 10⁸

(d)

5 x 10²

The wavelength of electromagnetic wave produced by Hertz experiment was _____________.

(a)

6mm

(b)

60m

(c)

6000 mm

(d)

60 cm

10.

Which of the following E.M waves has the longest wavelength?

(a)

Radio waves

(b)

(c)

X-rays

(d)

visible

11.

A moving coil galvanometer shows a deflection of 10° for a current of 0.7 mA. For another current, if the deflection is 15°, then the value of current is ______

(a)

10.5 mA

(b)

1.05 mA

(c)

0.35 mA

(d)

3.5 mA

12.

To draw thermo electric diagrams Lead is used as one of the metals to form a thermo couple with other metal because _______

(a)

It is a hard metal

(b)

It has high nuclear density

(c)

It does not allow X-rays

(d)

It has zero Thomson effect

13.

Fuse wire is an alloy of _________________.

(a)

lead and tin

(b)

tin and copper

(c)

lead and copper

(d)

lead and iron

14.

Bohr magneton is given by the formula is __________________.

(a)

\(\frac { neh }{ 4\pi m } \)

(b)

\(\frac { meh }{ 4\pi } \)

(c)

\(\frac { 4\pi m }{ en } \)

(d)

\(\frac { 4\pi e }{ mh } \)

15.

When the hot and cold junctions of a thermo couple are interchanged then the thermo emf ________________.

(a)

increases

(b)

remain unchanged

(c)

decreases

(d)

increases or decreases according to nature of metals used

16.

Melting point of tungsten is about heating element ________________.

(a)

3830°C

(b)

2380°C

(c)

3380°C

(d)

3803°C

17.

The voltage drop across the resistor in a LCR series circuit is __________________

(a)

V_R = IR

(b)

V_R = IR₂

(c)

V_R = I/R

(d)

V_R=R/I

18.

Cyclotron is used to _______________.

(a)

accelerate charged particles or ions to low voltages

(b)

decelerate charged particles or ions to high voltages

(c)

accelerate charged particles or ions to high energies

(d)

accelerate charged particles or ions to high voltages

19.

Potentiometer is an instrument used for the measurement of____________

(a)

current

(b)

resistance

(c)

capacitance

(d)

potential difference

20.

The quantity that changes with time in an A.C current is ________________.

(a)

magnitude

(b)

direction

(c)

both magnitude and direction

(d)

none

21.

The temperature coefficient of resistance increases for the metals when________

(a)

the temperature increases

(b)

the temperature decreases

(c)

does not depend upon the temperature

(d)

either (a) or (b)

22.

If two coils are wound on a soft iron core the mutual induction is ______________.

(a)

small

(b)

very large

(c)

infinity

(d)

zero

23.

The unit henry can also be written as ______________.

(a)

VS A^-1

(b)

Wb A^-1

(c)

Ωs

(d)

all

24.

A potential of 1 kV is applied between the ends of conductor of length 20 cm. The drift velocity of electron in this field is 3.52 x 10⁶ m/s. The relaxation time for the free electrons is

(a)

2 nano sec

(b)

4 nano sec.

(c)

6 nano sec

(d)

8 nano sec.

25.

The electric field intensity at a short distance r from uniformly charged infinite plane sheet of charge is

(a)

proportional to r

(b)

proportional to \(\frac{1}{2r}\)

(c)

proportional to \(\frac{1}{r^2}\)

(d)

independent of r

26.

The thermistors are usually made of ________________.

(a)

metals with low temperature coefficient of resistivity

(b)

metals with high temperature coefficient of resistivity

(c)

metal oxides with high temperature coefficient of resistivity

(d)

semi conducting materials with low temperature coefficient of resistivity

27.

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

28.

How many 160 \(\Omega \) resistor in parallel are required to carry a current of 5 A on a 100 V line?

(a)

(b)

(c)

(d)

29.

Capacitors use the principle of ________.

(a)

self induction

(b)

mutual induction

(c)

electrostatic induction

(d)

dielectric polarisation

30.

Charge Q on a capacitor varies with voltage V as shown in graph, where Q is along X-axis and V along Y-axis. The area of triangle OAB represents

(a)

capacitance

(b)

capacitive reactance

(c)

magnetic field between the plates

(d)

energy stored in the capacitor

31.

In a parallel plate capacitor of capacitance C, a metal sheet is inserted between the plates, parallel to them. The thickness of the sheet is half of the separation between the plates. The capacitance now becomes

(a)

(b)

\(\frac{C}{4}\)

(c)

(d)

\(\frac{C}{2}\)

32.

The unit for electric susceptibility is

(a)

Nm² C^-2

(b)

C² N^-1 m^-2

(c)

C^-2Nm²

(d)

N^-1 m^-2C²

33.

The magnitude of torque on dipole is maximum if

(a)

θ = 0^o

(b)

θ = 90^o

(c)

θ = 180^o

(d)

θ = 270^o

34.

Two condensers (capacitors) of capacity C₁ and C₂ are connected in parallel. A charge Q given to then is shared. The ratio of the charges Q is _________

(a)

\(\frac { { C }_{ 2 } }{ { C }_{ 1 } } \)

(b)

\(\frac { { C }_{ 1 } }{ { C }_{ 2 } } \)

(c)

C₁.C₂

(d)

\(\frac { 1 }{ { C }_{ 1 }\times { C }_{ 2 } } \)

35.

Eight mercury droplets having a radius of 1 mm and charge of 0.066 PC each merge to form one droplet. Its potential is _____________

(a)

2.4 V

(b)

1.2 V

(c)

3.6 V

(d)

4.8 V

36.

An uncharged metal sphere is placed between two equal and oppositely charged metal plates. The nature of lines of force will be ______________

(a)

(b)

(c)

(d)

37.

The given figure is a plot of lines of force due to two charges q₁ & q₂ find out the sign of charges

(a)

both negative

(b)

both positive

(c)

upper positive and lower negative

(d)

upper negative and lower positive

38.

The value of constant 'K' in coulomb law is _____________.

(a)

0.9 x 10⁹ Nm² C²

(b)

9 x 10^-9 Nm²C²

(c)

9 x 10⁹ Nm^-2 C^-2

(d)

9 x 10⁹ Nm² C^-2

39.

Two short bar magnets have magnetic moments 1.20 Am² and 1.00 Am² respectively. They are kept on a horizontal table parallel to each other with their north poles pointing towards south. They have a common magnetic equator and are separated by a distance of 20.0 cm. The value of the resultant horizontal magnetic induction at the mid-point O of the line joining their centres is (Horizontal components of Earth’s magnetic induction is 3.6 × 10^–5 Wb m^–2 )

(a)

3.60 × 10^-5 Wb m^-2

(b)

3.5 × 10^-5 Wb m^-2

(c)

2.56 × 10^-4 Wb m^-2

(d)

2.2 × 10^-4 Wb m^-2

40.

The BH curve for a ferromagnetic material is shown in the figure. The material is placed inside a long solenoid which contains 1000 turns/cm. The current that should be passed in the solenoid to demagnetize the ferromagnet completely is _____.

(a)

1.00 m A

(b)

1.25 mA

(c)

1.50 mA

(d)

1.75 mA

41.

A wire of length l carrying a current I along the Y direction is kept in a magnetic field is given by \(\vec { B } =\frac { \beta }{ \sqrt { 3 } } =(\hat { i } +\hat { j } +\hat { k } )T.\) The magnitude of Lorentz force acting on the wire is _____.

(a)

\(\sqrt { \frac { 2 }{ { 3 } } } \beta Il\)

(b)

\(\sqrt { \frac { 1 }{ { 3 } } } \beta Il\)

(c)

\(\sqrt { 2 } \beta Il\)

(d)

\(\sqrt { \frac { 1 }{ 2 } } \beta Il\)

42.

\(\frac{20}{\pi^2}H\) inductor is connected to a capacitor of capacitance C. The value of C in order to impart maximum power at 50 Hz is

(a)

50 μF

(b)

0.5 μF

(c)

500 μF

(d)

5 μF

43.

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)

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

44.

Two points A and B are maintained at a potential of 7 V and -4 V respectively. The work done in moving 50 electrons from A to B is _______.

(a)

8.80 x 10^-17 J

(b)

-8.80 x 10^-17 J

(c)

4.40 x 10^-17 J

(d)

5.80 x 10^-17 J

45.

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

46.

Which charge configuration produces a uniform electric field?

(a)

point charge

(b)

uniformly charged infinite line

(c)

uniformly charged infinite plane

(d)

uniformly charged spherical shell

47.

In Joule’s heating law, when R and t are constant, if the H is taken along the y axis and I² along the x axis, the graph is ______.

(a)

straight line

(b)

parabola

(c)

circle

(d)

ellipse

48.

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

49.

Two wires of A and B with circular cross section made up of the same material with equal lengths. Suppose R_A = 3 R_B, then what is the ratio of radius of wire A to that of B?

(a)

(b)

\(\sqrt3\)

(c)

\(\frac{1}{\sqrt3}\)

(d)

\(\frac{1}{3}\)

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Answers Key:

Multiple Choice Question

49 x 1 = 49

(b)
everything except green

(b)
absorbing substance

(d)
continuous

(b)
temperature

(a)
IR photographs

10.

(a)
Radio waves

11.

(b)
1.05 mA

12.

(d)
It has zero Thomson effect

13.

(a)
lead and tin

14.

(a)
\(\frac { neh }{ 4\pi m } \)

15.

(b)
remain unchanged

16.

17.

(a)
V_R = IR

18.

19.

(a)
current

20.

(b)
direction

21.

(a)
the temperature increases

22.

(b)
very large

23.

(d)
all

24.

(b)
4 nano sec.

25.

(d)
independent of r

26.

27.

(a)
will be doubled

28.

(d)
8

29.

30.

(d)
energy stored in the capacitor

31.

(a)
2C

32.

(b)
C² N^-1 m^-2

33.

(b)
θ = 90^o

34.

(b)
\(\frac { { C }_{ 1 } }{ { C }_{ 2 } } \)

35.

(a)
2.4 V

36.

37.

(a)
both negative

38.

(d)
9 x 10⁹ Nm² C^-2

39.

40.

41.

\(\vec { B } =\frac { \beta }{ \sqrt { 3 } } =(\hat { i } +\hat { j } +\hat { k } )T\)
Using an equation,
Lorentz force, \(\vec{F}=Il\hat{j}\times\vec B\)
We can get,
Lorentz force \(F=\sqrt { \frac { 2 }{ { 3 } } } \beta Il\)

42.

\(L=\frac{20}{\pi^2} \mathrm{H}, \mathrm{f}=50 \mathrm{~Hz} \)
\(f=\frac{1}{2 \pi \sqrt{L C}} \)
\(50=\frac{1}{2 \pi \sqrt{\frac{20}{\pi^2} \times C}} \)
\(50=\frac{1}{2 \times \sqrt{20 C}} \)
\(\therefore(50)^2=\frac{1}{4 \times 20 C} \)
\(\therefore C=\frac{1}{2500 \times 4 \times 20}=5 \times 10^{-6}=5 \mu \mathrm{F}\)

43.

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

44.

W = qV
V = 7 - (-4) = 11 V
q = ne = 50 x 1.6 x 10^-19 = 8 x 10^-18C
W = 8 x 10^-18 x 11 = 88 x 10^-18 = 8.8 x 10^-17]

45.

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

46.

47.

(a)
straight line

48.

R_t = R_o [1 + α(T₂ - T₁)
2 = 1[1 + 0.00125(T₂ - 293)
I = 5/4 x 10^-3(T₂ - 293)
T₂ = 1093 K
T₂ = 820 ^oC

49.

\(R \propto \frac{1}{A}, R \propto \frac{1}{r^2} \)
\(R_A \propto \frac{1}{r_A^2}, R_B \propto \frac{1}{r_B^2} \)
\(\frac{r_A}{r_B}=\left(\frac{R_B}{R_A}\right)^{1 / 2}=\left(\frac{R_B}{3 R_B}\right)^{1 / 2}=\frac{1}{3^{\frac{1}{2}}}=\frac{1}{\sqrt{3}}\)