# Physics - in Hindi

The number of images of an object placed between two mirrors inclined at an angle of 45o are:?

एक वस्तु 45o कोण पर झुके हुए दो दर्पणों के बीच रखी हैं इस वस्तु के कितने प्रतिबिंब होगें ??

A)
5

B)
6

C)
7

D)
8

7

Explanation :

If two plane mirrors are inclined at angle x, then the number of images formed in them is given by the formula:

Number of images formed = ( 360° /x ) - 1

By substituting the different values of angles between two inclined mirrors we can tabulate the number of images formed as follows:

 Angle between the two mirrors Number of images formed 45° 7 60° 5 90° 3 120° 2 180° 1 0° Infinite

A steel wire has a magnetic movement M. If the wire is bend into semicircular arc, The new magnetic movement becomes?

एक स्टील के तार में एक चुंबकीय आधुर्ण M है। यदि तार अर्धवृत्ताकार चाप में मोड़ दिया जाता है, तो नया चुंबकीय आधुर्ण होगा?

A)
M

B)
2M

C)
2πM

D)
(2/π)*M

(2/π)*M

Explanation : Let 2L = length of the bar magnet , then
magnetic moment,M = m * 2L

After bent into semicircle
πR = 2L (as circumference of a semi-circle = πR + 2*R )
R = 2L / π

When the magnet is bent in the form of a semicircle, the distance between the poles = 2R = 2 * (2L / π)

New magnetic moment = m * 2 * (2L / π) = 2M / π

The surface of a spherical shell is uniformly charged. Then what is the electric field inside the spherical shell?

एक गोलाकार खोल की सतह समान रूप से आवेशित है। फिर गोलाकार खोल के अंदर विद्युत क्षेत्र क्या है?

A)
Zero
/
शून्य

B)
constant
/
स्थिर

C)
Infinite
/
अनंत

D)
Proportional to the distance from the center
/
केंद्र से दूरी के समानुपाती

Zero

Explanation :

According to Gauss law all charges are distributed on the surface of the spherical shell. Therefore there will be no electric flux inside the spherical shell,So that the electric field inside the shell will be zero.

A wire of resistance R is stretched to reduce its diameter to half of its original value, The new resistance is?

प्रतिरोध R का एक तार इस तरह से खींचा कि इसका व्यास उसके प्रारंभिक मान से आधा हो गया है, नया प्रतिरोध होगा?

A)
2R

B)
4R

C)
8R

D)
16R

16R

Explanation :

The resistance R of a uniform cylinder of length L, of cross-sectional area A, and made of a material with resistivity ρ

R = ρL/A

New area = pi *(r/2)*(r/2)=1/4 of original area

As volume = length * area
new length = 4 * original length

New resistance R1 = ρ 4L/(A/4) = ρ 16*L/A = 16 R

The resistivity of the material depends on?

पदार्थ की प्रतिरोधकता निर्भर करती है?

A)
Length of the wire
/
तार की लंबाई

B)
Diameter of the wire
/
तार के व्यास

C)
Temperature of the wire
/
तार के तापमान पर

D)
Material of the wire
/
तार के पदार्थ पर

Material of the wire

Explanation :

The resistance R of a uniform cylinder of length L, of cross-sectional area A, and made of a material with resistivity ρ

Resistance R = ρL/A

The resistivity of a material depends on its nature and the temperature of the conductor, but not on its shape and size. A good conductor has less resistivity, whereas a bad conductor or insulator has high resistivity.
The unit for resistivity is the ohm-metre.

Calculate the energy equivalent of 1g of substance ?

1g पदार्थ के बराबर ऊर्जा की गणना करें?

A)
3*1013 J

B)
6*1013 J

C)
9*1013 J

D)
2*1013 J

9*1013 J

Explanation :

As per Einstein's equation E=mc2, where c is the speed of light (~3x108 m/s), m is the mass, and E is amount of energy.
1 g = 0.001 kg

E=0.001kg * (3 * 108 m/s)2
E=0.001 * 9 * 1016 kg*m2/s2
E=9 * 1013 kg*m2/s2

A kg*m2/s2 is a joule that measures energy

The unit of Thermal Conductivity of a material is?

किसी पदार्थ की ऊष्मीय चालकता की इकाई है?

A)

W / mK

B)

W / m2K

C)

Wm / K

D)

W2K / m

W / mK

Explanation :

In SI units, thermal conductivity is measured in watts per meter-kelvin (W / mK).

The most common element used in manufacturing of transistor is?

ट्रांजिस्टर के निर्माण में प्रयुक्त सबसे आम तत्व है?

A)

Silicon

B)

Phosphorus

C)

Gallium

D)

Germanium

Silicon

Explanation :

Transistor, three-terminal, solid-state electronic device used for amplification and switching.

The first transistors were made from germanium, but now most transistors are made from silicon. Silicon (Si) and germanium (Ge) form similar crystal structures with similar physical properties, but silicon is preferred over germanium because of silicon's superior thermal characteristics.

A larger force on a rotating body results in larger?

घूर्णन करने वाली वस्तु पर लगाये गये एक बड़े बल का परिणाम बड़े .................में होता है?

A)

mass

B)

torque

C)

axis of rotation

D)

centre of mass

torque

What is the unit of the physical quantity, magnetic flux density?

भौतिक मात्रा, चुंबकीय प्रवाह घनत्व की इकाई क्या है?

A)

Siemens

B)

Weber

C)

Henry

D)

Tesla