Physics Class 12 Mini Mock - 1 - Free MCQ Practice Test with solutions,

In a concave mirror, the reflecting surface is the inner surface of a hollow sphere, that is, the surface facing towards the centre of the sphere. When a hollow sphere is cut and its outer surface painted, the inner surface acts as the reflecting surface, forming a concave mirror. This type of mirror is also known as a converging mirror because it reflects light to converge at a point.

Therefore, the correct option is Reflecting surface is towards the centre of the sphere of which it can be considered as a cut off portion, which is option a.

Control rods are used in nuclear reactors to control the fission rate of uranium and plutonium. They are composed of chemical elements such as boron, silver, indium and cadmium that are capable of absorbing many neutrons without themselves fissioning.

A point charge is single dimensional. The three dimensional imaginary enclosed surface of a point charge will be sphere.

Definition based

e = NBAω = 20 x 3 x 10^-2 x (3.14 x 0.08 x 0.08) x 50 = 0.603C

average power loss due to joule heating

By Faraday's Ist Law
Amount deposited (m) = Zit = Zq
m ∝ q
Amount deposited is directly proportional
to charge.

Definition based

Case 1:- In figure 1 if FE​=FB​ ⇒ particle will always move in a straight line.(option (iii))
Case 2:- In figure 2 particle will always move in a straight line.(option (ii))

a car battery of 12V provides a current of about 200A, which is the current needed to operate a starter motor. So a battery has a very small internal resistance.
also,The cause of non-correctable battery problems and.A weak cell holds less capacity and is discharged more quickly.

Nucleus of hydrogen has only one proton. Hence its binding energy will be zero. The nuclear binding energy is the energy it takes to separate all the nucleons in a nucleus from each other. Since there is only the one nucleon, it's already separated from any other nucleons.

The coil of a galvanometer is wound on a light metallic frame (such as aluminium). When the coil rotates in the magnetic field of the permanent magnet, eddy currents are induced in the metallic frame. These eddy currents create magnetic fields that oppose the motion of the coil (according to Lenz's Law), thus providing electromagnetic damping. This damping helps the coil to return to zero quickly and prevents oscillations.

The plum pudding model is one of several scientific models of the atom. According to J.J. Thomson atomic models the positive particles in the atom form something like the "batter" in a plum pudding, while the negative electrons are scattered through this "batter".

Magnification in microscope is  m=− lD/f₀​​f_e
where, l is length of tube and D is least distance for clear vision
f_0​ is focal length of objective
fe​ is the focal length of the eyepiece.
So, as l increases m increases.
Hence, the magnifying power of a microscope increases with increase in tube length.
 

Rutherford Alpha Particle Scattering Experiment.Rutherford directed beams of alpha particles (which are the nuclei of helium atoms and hence positively charged) at thin gold foil to test this model and noted how the alpha particles scattered from the foil.

Potential at the centre of the sphere
= potential on the surface = 80 V.

Q = It also Q = ne [e = 1.6 × 10⁻¹⁹C]
∴ ne = It or
= 6.25 × 10¹⁸ electrons s⁻¹

We know that
1/λ​=R(1/n²​₁​−1/n²₂​​)
1/λ=R(1/2²) − (1/3²​)⇒R(1/4)−(1/9​)
1/λ​=(9−4​/36)R=5R​/36⇒λ=36​/5R

 Suppose the angle between the transmission axes of the analyser and the polarizer is θ. The completely plane polarized light form the polarizer is incident on the analyser. If E₀ is the amplitude of the electric vector transmitted by the polarizer, then intensity I₀ of the light incident on the analyser is
I ∞ E₀²
 
The electric field vector E₀ can be resolved into two rectangular components i.e E₀ cosθ and E₀ sinθ. The analyzer will transmit only the component ( i.e E₀ cosθ ) which is parallel to its transmission axis. However, the component E₀sinθ will be absorbed by the analyser. Therefore, the intensity I of light transmitted by the analyzer is,
 
I ∞ ( E₀ x cosθ )²
 
I / I₀ = ( E₀ x cosθ )² / E₀² = cos2θ
 
I = I₀ x cos²θ
when light passes from polarizer it's intensity becomes half and when passed through analyser it becomes,
I = I₀ x cos²θ/2
 

Second excited state corresponds to n = 3

Electric field lines are essential for understanding various aspects of electric fields. They illustrate:

• Field strength: The density of lines indicates how strong the electric field is; closer lines mean a stronger field.
• Direction: The arrows on the lines show the direction a positive charge would move within the field.
• Nature of charge: Lines emanate from positive charges and terminate at negative charges, visually representing their nature.

These characteristics together provide a comprehensive view of the electric field's behaviour and effects.

Collisions between charged particles emitted from cathode and atoms of gas.The discharge of electricity through liquefied gases is an interesting phenomenon which can be systematically studied with the help of a discharge tube.In discharge tube collision between charged particles emitted from cathode and atoms of the gas results to colorless glow in tube.

f_a = 0.15 m,μ_g = 3/2,f_e = 0.225+0.15
From lens formula,

Energy of photon of X-rays is more than
energy of photon of ultraviolet rays. Because
frequency of X rays is more than ultraviolet
rays.

The speed of electromagnetic waves in free space depends on two important properties: permeability and permittivity. In this context:

• μ₀ represents the permeability of free space, which indicates how well magnetic fields can pass through a vacuum.
• ε₀ signifies the permittivity of free space, reflecting how electric fields interact with the vacuum.

These properties are fundamental to understanding how electromagnetic waves propagate in free space.

The image will be virtual, upright and diminished.

A current-carrying wire produces a magnetic field, as described by Biot-Savart’s law. The reverse effect, where a magnetic field generates an electric current, was discovered by Michael Faraday and is known as Faraday's Law of Electromagnetic Induction.

Faraday demonstrated this through an experiment: when a bar magnet is moved relative to a conducting loop connected to an ammeter (without any external emf source), a current is induced. Key observations include:

1. Current appears only when there is relative motion between the magnet and the loop.
2. Faster motion produces a stronger current.
3. The direction of current depends on the magnet’s motion (towards or away) and its pole orientation.

This induced current is caused by a change in magnetic flux, which is the number of magnetic field lines passing through the loop. The induced emf persists as long as the magnetic flux changes. The emf always opposes the change in flux, as per Lenz’s Law.

In conclusion, the process of producing induced current and emf is called electromagnetic induction. The correct answer is Option A.