Physics

View in English View in Hindi

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

A)
5

B)
6

C)
7

D)
8


Correct Answer :

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
Infinite

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

A)
M

B)
2M

C)
2πM

D)
(2/π)*M


Correct Answer :

(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?

A)
Zero

B)
constant

C)
Infinite

D)
Proportional to the distance from the center


Correct Answer :

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?

A)
2R

B)
4R

C)
8R

D)
16R


Correct Answer :

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 radius = r/2
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?

A)
Length of the wire

B)
Diameter of the wire

C)
Temperature of the wire

D)
Material of the wire


Correct Answer :

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 ?

A)
3*1013 J

B)
6*1013 J

C)
9*1013 J

D)
2*1013 J


Correct Answer :

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?

A)

W / mK


B)

W / m2K


C)

Wm / K


D)

W2K / m



Correct Answer :

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?

A)

Silicon


B)

Phosphorus


C)

Gallium


D)

Germanium



Correct Answer :

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?

A)

mass


B)

torque


C)

axis of rotation


D)

centre of mass



Correct Answer :

torque

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

A)

Siemens


B)

Weber


C)

Henry


D)

Tesla



Correct Answer :

Tesla


Explanation :

The tesla (symbol T) is a derived unit of the magnetic induction (also, magnetic flux density) in the International System of Units. One tesla is equal to one weberper square metre.

Latest Updates

Trigonometry

What is the value of cot 4π/3 ?

Indian Politics

Article-24 of the Indian Constitution ‘Prohibition of employment of children in factories, etc’ deals with?

Article-134A of the Indian Constitution ‘Certificate for appeal to the Supreme Court’ deals with?

Chemistry

Who invented Aspirin?

Physics

A larger force on a rotating body results in larger?

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

Algebra

The system of equations 2x + 4y = 6 and 4x + 8y = 8 is ?

Time and Distance

A thief is spotted by a policeman from a distacne of 100 m. When the policeman starts the chase, the thief also starts running. If the speed of the theif is 8 km / hour and that of the policeman is 10 km/hour, then how far will the theif have to run before he is overtaken?

Algebra

Aman and Alok attempted to solve a quadratic equation. Aman made a mistake in writing down the constant term and ended up in roots (4, 3). Alok made a mistake in writing down the coefficient of x to get roots (3, 2). The correct roots of the equation are?

Compound Interest

The effective annual rate of interest corresponding to a nominal rate of 22% per annum payable half-yearly is?

Volume and Surface Area

If the volume of a cylinder is 2156 cubic cm and height is 14 cm, find its radius?

Algebra

What is the equation of the line which passes through the points (2, 3) and (- 4, 1)?

Triangles

In △ABC, the angle bisector of ∠A cuts BC at E. Find length of AC, if lengths of AB, BE and EC are 9 cm, 3.6 cm and 2.4 cm?

In a triangle, the length of the opposite side of the angle which measures 45° is 8√2 cm, what is the length of the side opposite to the angle which measures 90°?

General Knowledge of India

The boundary line between India and Pakistan is called?

Which city is located on the banks of the river Mahanadi?

Indian History

When was the battle of Haldighati fought?

In 1498, which Portuguese explorer discovered a new sea route from Europe to India?

General Knowledge of India

Chapchar Kut is a festival of which State?

Chemistry

In chemistry, soap is a salt of a ?

Indian Economy

Which of the following is a Direct tax?

Biology

Sauria lacertidae is the scientific name of?

Which of the following is a primary function of haemoglobin?

Average

A factory buys 8 machines.3 Machine A, 2 Machine B and rest Machine C. Prices of the machines are 100000, 80000 and 45000 respectively.Calculate the average cost of these machines?

Discount

Ticket for an adult is 500 and a child is 200. 1 child goes free with two adults. If a group has 20 adults and 8 children what will be the discount the group get?