List of top Physics Questions

In an experiment of CE configuration of n–p–n transistor, the transfer characteristics are observed as given in figure. 

In an experiment of CE configuration of n–p–n transistor

If the input resistance is 200 Ω and output resistance is 60 Ω, the voltage gain in this experiment will be______.

Resistances are connected in a meter bridge circuit as shown in the figure. The balancing length l1 is 40 cm. Now an unknown resistance x is connected in series with P and new balancing length is found to be 80 cm measured from the same end. Then the value of x will be ________ Ω.
meter bridge circuit
The effective current I in the given circuit at very high frequencies will be ______ A.
The effective current I in the given circuit
Two coils require 20 minutes and 60 minutes respectively to produce same amount of heat energy when connected separately to the same source. If they are connected in parallel arrangement to the same source; the time required to produce same amount of heat by the combination of coils, will be ___ min.

The intensity of the light from a bulb incident on a surface is 0.22 W/m2. The amplitude of the magnetic field in this light-wave is ___ × 10–9 T.

(Given : Permittivity of vacuum ε0 = 8.85 × 10–12C2N–1–m–2, speed of light in vacuum c = 3 × 108 ms–1)

As per the given figure, two plates A and B of thermal conductivity K and 2 K are joined together to form a compound plate. The thickness of plates are 4.0 cm and 2.5 cm, respectively and the area of cross-section is 120 cm2 for each plate. The equivalent thermal conductivity of the compound plate is \((1+\frac{5}{α})K,\) then the value of α will be ___.

As per the given figure, two plates A and B of thermal conductivity K and 2 K are joined together to form a compound plate

In the hydrogen spectrum, λ be the wavelength of first transition line of Lyman series. The wavelength difference will be “aλ” between the wavelength of 3rd transition line of the Paschen series and that of 2nd transition line of Balmer series where a = ______.
A body is performing simple harmonic with an amplitude of 10 cm. The velocity of the body was tripled by air jet when it is at 5 cm from its mean position. The new amplitude of vibration is \(\sqrt x\) cm. The value of x is ___.
The variation of applied potential and current flowing through a given wire is shown in figure. The length of wire is 31.4 cm. The diameter of wire is measured as 2.4 cm. The resistivity of the given wire is measured as x × 10–3Ω cm. The value of x is____. [Take π = 3.14]
In the circuit shown below, maximum Zener diode current will be ________ mA.
circuit for maximum Zener diode current
Two streams of photons, possessing energies equal to five and ten times the work function of metal are incident on the metal surface successively. The ratio of maximum velocities of the photoelectron emitted, in the two cases respectively, will be

Two coherent sources of light interfere. The intensity ratio of two sources is 1 : 4. For this interference pattern if the value of
\(\frac{I_{max}+I_{min}}{I_{max}-I_{min}}\)is equal to \(\frac{2α+1}{β+3},\)
then α/β will be

A block of mass 40 kg slides over a surface, when a mass of 4 kg is suspended through an inextensible massless string passing over a frictionless pulley as shown below.
The coefficient of kinetic friction between the surface and block is 0.02. The acceleration of the block is (Given g = 10 ms–2)
A block of mass 40 kg slides over a surface
Time period of a simple pendulum in a stationary lift is ‘T’. If the lift accelerates with \(\frac{g}{6}\) vertically upwards then the time period will be (Where g = acceleration due to gravity)

Two bodies of masses m1 = 5 kg and m2 = 3 kg are connected by a light string going over a smooth light pulley on a smooth inclined plane as shown in the figure. The system is at rest. The force exerted by the inclined plane on the body of mass m1 will be
[Take g = 10 ms–2]

Two bodies of masses m1 = 5 kg and m2 = 3 kg are connected by a light

A square wave of the modulating signal is shown in the figure. The carrier wave is given by C(t) = 5 sin(8πt) Volt. The modulation index is

Fig.

Two long parallel conductors \(S_1\) and \(S_2\) are separated by a distance \(10\) cm and carrying currents of \(4\) A and \(2\) A respectively. The conductors are placed along x-axis in X–Y plane. There is a point P located between the conductors (as shown in figure). A charge particle of \(3π\) coulomb is passing through the point P with velocity \(\overrightarrow v=(2\hat i+3\hat j)\) m/s; where \(\hat i\) and \(\hat j\) represents unit vector along x & y axis respectively. The force acting on the charge particle is \(4π×10^{−5}(−x\hat i+2\hat j)N\). The value of x is:
The conductors are placed along x-axis in X–Y plane. There is a point P located between the conductors

One end of a massless spring of spring constant k and natural length \(l_0\) is fixed while the other end is connected to a small object of mass \(m\) lying on a frictionless table. The spring remains horizontal on the table. If the object is made to rotate at an angular velocity \(ω\) about an axis passing through fixed end, then the elongation of the spring will be :

Identify the correct statements from the following descriptions of various properties of electromagnetic waves.
(A) In a plane electromagnetic wave electric field and magnetic field must be perpendicular to each other and direction of propagation of wave should be along electric field or magnetic field.
(B) The energy in electromagnetic wave is divided equally between electric and magnetic fields.
(C) Both electric field and magnetic field are parallel to each other and perpendicular to the direction of propagation of wave.
(D) The electric field, magnetic field and direction of propagation of wave must be perpendicular to each other.
(E) The ratio of amplitude of magnetic field to the amplitude of electric field is equal to speed of light.

Choose the most appropriate answer from the options given below

The velocity of the bullet becomes one third after it penetrates 4 cm in a wooden block. Assuming that bullet is facing a constant resistance during its motion in the block. The bullet stops completely after travelling at (4 + x) cm inside the block. The value of x is

A beam of light travelling along X-axis is described by the electric field Ey = 900sin ω(t – x/c). The ratio of electric force to magnetic force on a charge q moving along Y-axis with a speed of 3 × 107 ms–1 will be :
(Given speed of light = 3 × 108 ms–1)

A logic gate circuit has two inputs A and B and output Y. The voltage waveforms of A, B and Y are shown below.
 

Fig. Logic gate circuit


The logic gate circuit is :

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: Alloys such as constantan and manganin are used in making standard resistance coils.
Reason R: Constantan and manganin have very small value of temperature coefficient of resistance.
In the light of the above statements, choose the correct answer from the options given below.
For a transistor to act as a switch, it must be operated in
An npn transistor with current gain \(β = 100\) in common emitter configuration is shown in the figure. The output voltage of the amplifier will be
npn transistor with current gain