List of top Physics Questions

In semiconductors at a room temperature

In an intrinsic semiconductor:

In an equilateral triangle $A B C, F_{1}, F_{2}$ and $F_{3}$ are three forces acting along the sides $A B, B C$ and $A C$ as shown in the given figure. What should be the magnitude of $F_{3}$ so that the total torque about $O$ is zero?

At absolute zero temperature, semiconductor behaves as a/an:

A perfectly black body is one where

A particle moves from position $r_1 = 3 \hat i + 2 \hat j - 6 \hat k$ to position $r_2 = 14 \hat i + 13 \hat j + 9 \hat k$ under action of force $F = 4 \hat i + \hat j + 3 \hat k$ N. The work done will be

If $\vec{A} \times \vec{B}|=| \vec{A} \cdot \vec{B} \mid$ then the angle between $\vec{A}$ and $\vec{B}$ will be :

If $\left|\vec{A}+\vec{B}\right|=\left|\vec{A}-\vec{B}\right|$, then the angle between $\vec{A}$ and $\vec{B}$ will be

Two open organ pipes of length $25\, cm$ and $25.5\, cm$ produce $0.1$ beat/sec. The velocity of sound will be :

Which one of the following is different from others?

A man of weight $ 75\,kg $ is standing in an elevator which is moving with an acceleration of $5\,m/s^{2}$ in upward direction the apparent weight of the man will be: $ (g=10\,m/s^{2})$

In Bohr?s model, the atomic radius of the first orbit is $r_0$ . The radius of the third orbit, is

In achromatic combination of lenses is formed by joining :

A machine gun fires a bullet of mass 40 g with a velocity 1200 $ms^{-1}$. The man holding it can exert a maximum force of 144 N on the gun. How many bullets can he fire per second at the most ?

A light ray is incident perpendicular to one face of a $90^{\circ}$ prism and is totally internally reflected at the glass-air interface. If the angle of reflection is $45^{\circ}$, we conclude that the refractive index $n$

If the pressure of a gas contained in a vessel is increased by $0.4\%$ when heated through $1^{\circ}C$, the initial temperature had been :

For a given angle of projection, if the time of flight of a projectile is doubled, the horizontal range will increase to :

A fire screen produces sensation of cooling as :

A concave mirror of focal length $15 \,cm$ forms an image having twice the linear dimension of the object. The position of the object when die image is virtual will be :

The velocity of bullet is reduced from $200\, m / s$ to $100 \,m / s$ while travelling through a wooden block of thickness of $10 \,cm$. The retardation assuming to be uniform, will be :

A fireman wants to slide down a rope. The breaking load for the rope is $\frac{3}{4}$th of the weight of the man. With what acceleration should the fireman slide down? (Acceleration due to gravity is g)

A current $i$ ampere flows along an infinitely long straight thin walled tube, then the magnetic induction at any point inside the tube is

A coil having n turns and resistance $4R\, O$. This combination is moved in time t seconds from a magnetic field $W_1$ weber to $W_2$ weber. The induced current in the circuit is

A streched string vibrates with a fundamental frequency of $200$ Hz. If its mass per unit length were to be doubled. What would be the frequency of the first harmonic ?

The intensity of sound from a radio at a distance of $2$ meters from its speaker is $1 \times 10^{-2} \mu W/m^2$. The intensity at a distance of $10$ meters would be