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

1.

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

2.

Chinese scientists have created the world's first autonomous _________ to combat caner tumours.

(a)

RNA Robot

(b)

DNA Robot

(c)

m RNA Robot

(d)

r RNA Robot

3.

Length contraction is known as ________

(a)

Gerner resolution

(b)

Thomson contraction

(c)

Compton effect

(d)

Lorentz-Fitzgerald contraction

4.

Energy gap between valence band and conduction band is called as the _____________

(a)

forbidden energy gap

(b)

conduction band gap

(c)

valence band gap

(d)

filled band gap

5.

The light photon has _______ nature.

(a)

wave

(b)

particle

(c)

matter

(d)

dual

6.

The most commonly, employed modulation in satellite communication is the _____________.

(a)

amplititude modulation

(b)

FM

(c)

phase modulation

(d)

all

7.

Most of the electron in the base of N-P-N transistor flow __________________.

(a)

out of the base lead

(b)

into the collector

(c)

into the emitter

(d)

into the base supply

8.

Why can't we physically join p-type and n-type semiconductor directly to form a p-n junction?

(a)

Inter-atomic spacing become less than 1 A^O

(b)

p -type will repet N-type

(c)

There will be discontinuity for the flowing charge carriers

(d)

Semi-conducting properties will be lost

9.

Bohr's radius gives the radius of the _________ orbit.

(a)

first

(b)

second

(c)

third

(d)

fourth

10.

The fig. represents the observed intensity of X-rays emitted by an X-ray tube as a function of wavelength. The sharp peaks A and B denote ____________.

(a)

continuous spectrum

(b)

band spectrum

(c)

characteristic spectrum

(d)

white radiations

11.

The materials used in Robotics are _____.

(a)

Aluminium and silver

(b)

Silver and gold

(c)

Copper and gold

(d)

Steel and aluminum

12.

For light incident from air on a slab of refractive index 2, the maximum possible angle of refraction is, ______.

(a)

30^o

(b)

45^o

(c)

60^o

(d)

90^o

13.

The frequency of electromagnetic radiation Hertz produced was _________ Hz.

(a)

10⁸

(b)

5x10⁷

(c)

3x10⁸

(d)

6x10⁵

14.

Calculate the current passing through a coil of diameter 20 cm, having 50 turns, when the field at the centre of the coil is 200 ampere-turns/ meter _______________.

(a)

80 ampere

(b)

1.6 ampere

(c)

0.8 ampere

(d)

160 ampere

15.

Joule's law is verified by using _____________.

(a)

Joule's calorimeter

(b)

Joule's voltmeter

(c)

Joule's galvanometer

(d)

thermometer

16.

An alternating current has _______________.

(a)

only positive value

(b)

only negative value

(c)

both positive and negative value

(d)

steady value

17.

The mobility of an electron is one million times less than that of its specific charge, the mean time taken between two successive collisions is_______

(a)

1ms

(b)

\(1\mu s\)

(c)

1nano sec

(d)

1giga sec

18.

The potentiometer wire is made of___________

(a)

Manganin

(b)

Copper

(c)

Aluminium

(d)

Nichrome

19.

When an electric dipole is placed in a uniform external electric field parallel to the field, it will experience_________.

(a)

a torque but no force

(b)

a force but no torque

(c)

a torque as well as a force

(d)

neither a force nor a torque

20.

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

21.

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

22.

Two identical coils, each with N turns and radius R are placed coaxially at a distance R as shown in the figure. If I is the current passing through the loops in the same direction, then the magnetic field at a point P at a distance of R/2 from the centre of each coil is _____.

(a)

\(\frac { 8N{ \mu }_{ ° }I }{ \sqrt { 5 } R } \)

(b)

\(\frac { 8N{ \mu }_{ ° }I }{ { 5 }^{ 3/2 }R } \)

(c)

\(\frac { 8N{ \mu }_{ ° }I }{ { 5 }R } \)

(d)

\(\frac { 4N{ \mu }_{ ° }I }{ \sqrt { 5 } R } \)

23.

A circular coil with a cross-sectional area of 4 cm² has 10 turns. It is placed at the centre of a long solenoid that has 15 turns/cm and a cross-sectional area of 10 cm². The axis of the coil coincides with the axis of the solenoid. What is their mutual inductance?

(a)

7.54 μH

(b)

8.54 μH

(c)

9.54 μH

(d)

10.54 μH

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 of resistance 2 ohms per meter is bent to form a circle of radius 1m. The equivalent resistance between its two diametrically opposite points, A and B as shown in the figure is