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12th Standard Physics English Medium Free Online Test One Mark Questions with Answer Key 2020 - Part Four

Published on: 12/10/2020

12th Standard Physics English Medium Free Online Test One Mark Questions with Answer Key 2020 Part Four

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

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Questions:

Multiple Choice Question

25 x 1 = 25

A concave mirror is used to focus the image of a flower on a nearby well 120 cm from the flower. If a lateral magnification of 16 is desired, the distance of the flower from the mirror should be _____________.

(a)

8 cm

(b)

12 cm

(c)

80 cm

(d)

120 cm

A diminished virtual image can be formed only in ______________.

(a)

Plane mirror parabolic mirror

(b)

A concave mirror

(c)

A convex mirror

(d)

concave

A point source of light B is placed at a distance L in front of the center of a mirror of width d hung vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror at a distance of 2 L front it as shown. The greatest distance over which he can see the image of the light source in the mirror is ___________.

(a)

d/2

(b)

(c)

(d)

The size of the Nano robots is reduced to ________ level to perform a task in very small space.

(a)

Macroscopic

(b)

Robots DNA

(c)

Microscopic

(d)

Bacteria

The maximum carrier swing allowed in frequency modulation is ________________.

(a)

455 kHz

(b)

10.7 kHz

(c)

75 MHz

(d)

150 kHz

The clocks in moving ships will appear to go _______ clocks on earth.

(a)

faster than

(b)

slower than

(c)

the same as

(d)

stops after leaving earth

The anode of a simple photo emissive cell is _______

(a)

glass tube

(b)

quartz crystal

(c)

platinum wire

(d)

iron rod

A charged oil drop is suspended in a uniform field of 3 x 10⁴ Vm^-1 so that it neither falls nor rises. The charge on the drop will be _____________.

(a)

3.3 x 10^-18C

(b)

3.2 x 10^-18C

(c)

1.6 x 10^-18C

(d)

4.8 x 10^-18C

A N-P-N transistor conducts when collector is _________ and emitter is ________ with respect to base.

(a)

positive, negative

(b)

positive, positive

(c)

negative, negative

(d)

negative, positive

10.

According to to Bohr, the relation between principal quantum number (n) and radius of the orbit (r) is _____________.

(a)

r α \(\frac1n\)

(b)

r α \(\frac{1}{n^2}\)

(c)

r α n

(d)

r α n²

11.

The alloys used for muscle wires in Robots are _____.

(a)

Shape memory alloys

(b)

Gold copper alloys

(c)

Gold silver alloys

(d)

Two dimensional alloys

12.

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

13.

The wavelength range of microwave is _______m

(a)

10^-8 to 0.35

(b)

10^-3 to 0.3

(c)

10^-8 to 10^-6

(d)

10^-3 to 10^-1

14.

Which of the following is a special aspect of EM wave?

(a)

can be deflected by electric field

(b)

can be deflected by magnetic filed

(c)

can be deflected by both electric & magnetic filed

(d)

none of these

15.

The direction of force on a current carrying conductor placed in a magnetic field is given by _____

(a)

Fleming's Left Hand Rule

(b)

Fleming's Right Hand Rule

(c)

Ampere's velocity

(d)

Biot-Savart Law

16.

When the current flowing in a circular coil is doubled and the number of turns of the coil in it is halved, the magnetic field at its center will become _____________.

(a)

four times

(b)

same

(c)

half

(d)

double

17.

The reactance of a capacitor is __________.

(a)

X_c= Cω

(b)

X_c = \(\frac{1}{Cω}\)

(c)

X_c = \(\frac{C}{ω}\)

(d)

X_c = \(\frac{ω}{C}\)

18.

In the case of Wheatstone's Bridge the bridge balance condition will be obtained only when____

(a)

the current through the galvanometer is maximum

(b)

the current through the galvanometer is minimum

(c)

the current through the galvanometer is zero

(d)

the current through the galvanometer is infinity

19.

An emf of 12V is induced when the current in the coil changes at the rate of 40 A S^-1. The coefficient of self induction of the coil is __________________.

(a)

0.3 H

(b)

0.003 H

(c)

30 H

(d)

4.8 H

20.

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

21.

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

22.

In a series RL circuit, the resistance and inductive reactance are the same. Then the phase difference between the voltage and current in the circuit is

(a)

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

(b)

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

(c)

\(\frac{\pi}{6}\)

(d)

zero

23.

Which one of them is used to produce a propagating electromagnetic wave?

(a)

an accelerating charge

(b)

a charge moving at constant velocity

(c)

a stationary charge

(d)

an uncharged particle

24.

A thin conducting spherical shell of radius R has a charge Q which is uniformly distributed on its surface. The correct plot for electrostatic potential due to this spherical shell is _____.

(a)

(b)

(c)

(d)

25.

A wire connected to a power supply of 230 V has power dissipation P₁. Suppose the wire is cut into two equal pieces and connected parallel to the same power supply. In this case power dissipation is P₂. The ratio \(\frac{P_2}{P_1}\) is ______.

(a)

(b)

(c)

(d)

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Answers Key:

Multiple Choice Question

25 x 1 = 25

(a)
8 cm

(d)
3d

(d)
150 kHz

(a)
faster than

(a)
3.3 x 10^-18C

(b)
positive, positive

10.

(d)
r α n²

11.

They are thin strands of wire made of shape memory alloys. They can contract by 5% when electric current is passed through them.

12.

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

13.

(b)
10^-3 to 0.3

14.

(d)
none of these

15.

(a)
Fleming's Left Hand Rule

16.

(b)
same

17.

(b)
X_c = \(\frac{1}{Cω}\)

18.

19.

(a)
0.3 H

20.

(a)
both negative

21.

22.

In RL circuit, tanΦ = \(\frac{X_l}{R}\)
If R = X₁, then tanΦ = \(\frac{X_l}{X_l}=1\)
∴ Φ = tan^-1(1)=\(\frac{\pi}{4}\)
∴ Phase difference \(=\frac{\pi}{4}\)

23.

(a)
an accelerating charge

24.

25.

\(\mathrm{V}=230 \mathrm{~V} \)
\(P=\frac{V^2}{R} \text { since } \mathrm{V} \text { is same } \mathrm{P} \propto \frac{1}{R} \)
\(\frac{1}{R_2}=\frac{1}{\frac{R_1}{2}}+\frac{1}{\frac{R_1}{2}}=\frac{2}{R_1}+\frac{2}{R_1}=\frac{2+2}{R_1} \)
\(\frac{1}{R_2}=\frac{4}{R_1} \)
\(\therefore R_2=\frac{R_1}{4} \)
\(R_1=4 R_2 \)
\(\therefore \frac{P_2}{P_1}=\frac{R_1}{R_2}=\frac{4 R_2}{R_2}=4\)