UP PGT Physics Mock Test - 1 - UPTET MCQ

CONCEPT:

• Conservative force: A force is conservative if the work done by the force in displacing an object from one point to another point is independent of the path followed by the object and depends only on the endpoints.
• Electrostatic forces, gravitational forces, elastic forces, magnetic forces, etc and are the examples of a conservative force.
• Non-conservative forces: A force is said to be non-conservative if work done by or against the force in moving a body from one position to another, depends on the path followed between these two positions.
• Example:  Frictional force, Viscous force, Airdrag, etc.

EXPLANATION:

• If a body of mass m lifted to height h from the ground level by a different path, then the work done in each case will be the same. Therefore, in conservative force work done by the force in displacing an object from one point to another point is independent of path followed by the object and depends only on the endpoints.

• If a body is moved from position A to another position B on a rough table, work done against frictional force shall depend on the length of the path between A and B and not only on the position A and B. Therefore, in non-conservative force work done by or against the force in moving a body from one position to another, depends on the path followed between these two positions.

Explanation:All collisions between molecules among themselves or between molecules and the walls are elastic. So that total kinetic energy and total momentum is conserved. Also the average properties of gas are remains constant.

Convection is the movement of surrounding medium according to density by which transfer of heat takes place. Whereas in option A it tells about the transfer of heat due to molecules inside conductor, which is conduction.

Modulus of rigidity is defined as the ratio of Shear stress to shear strain.

Maxwell’s Fourth Equation
It is based on Ampere’s circuital law. To understand Maxwell’s fourth equation it is crucial to understand Ampere’s circuital law,
Consider a wire of current-carrying conductor with the current I, since there is an electric field there has to be a magnetic field vector around it. Ampere’s circuit law states that “The closed line integral of magnetic field vector is always equal to the total amount of scalar electric field enclosed within the path of any shape” which means the current flowing along the wire(which is a scalar quantity) is equal to the magnetic field vector (which is a vector quantity)

Scalar quantity gives you an idea about how much of an object there is, but vector quantity gives you an indication of how much of an object there is and that also in which direction. So, the main difference between these two quantities is associated with the direction, i.e. scalars do not have direction but vectors do. 

Components connected in parallel provide alternative pathways for current flow. When cells are connected in parallel, the total voltages that they provide does not change. For example, when two or more 2 V cells are connected in parallel, they still provide a total voltage of 2 V.

Let us assume a force dF is applied at P in positive x - direction. This will stretch each spring by dl inducing a spring force dFs in each spring.

Let the static deformation of the system is dx (along the x-direction). The particle is in equilibrium. So,

Using Pythagoras theorem, 

Here y is constant. 

Changes(if required): The answer provided in the forum is wrong, The correct answer would be option B.
Solution:
Given,
V_R-rms =30.0V
V_C-rms=90.0V
V_L-rms=50.0V
To find the root mean square voltage across the source, we will use the formula,
V_rms=√[V_r²+(V_L-V_C)²]
=√[(30.0V)² +(50.0V-90.0V)²]
=50.0 V

The sole reason is 'refraction' in a single word. Refraction of waves involves a change in the direction of waves as they pass from one medium to another. Refraction, or the bending of the path of the waves, is accompanied by a change in speed and wavelength of the waves. Water waves travel fastest when the medium is the deepest. Thus, if water waves are passing from deep water into shallow water, they will slow down. But here it is traveling from shallow water to deep water, then the waves bend in the opposite direction.

In a simple pendulum the restoring force is due to the tangential component of the gravitational force because on applying torque equation on the radial forces the effect is nullified due to it passing from centre & only tangential component remains.

Assume the mirror is at the origin and it is moving about the origin along x direction between x = -2 and x = +2 as its extreme positions.
Assume that the object is placed at co=ordinate of x = - (2+x)
So, when mirror is at position x = -2, the object's image will be formed at x coordinate X = - 2+x 
And when the mirror is at position x = +2, the image is formed at X = 6+x 
So, the net difference in the position of image between these 2 co-ordinates is ( 6 + x  ) - ( -2 + x ) = 8
So, the amplitude will be half of this distance. So the answer is 8/2 = 4 cm. 
Option C is correct.
 

Bernoulli's theorem, in fluid dynamics, relation among the pressure, velocity, and elevation in a moving fluid (liquid or gas), the compressibility and viscosity (internal friction) of which are negligible and the flow of which is steady, or laminar.

The charged particle will move along the lines of electric field (and magnetic field). Magnetic field will exert no force. The force by electric field will be along the lines of uniform electric field. Hence the particle will move in a straight line.

From the first law of thermodynamics dQ = dU + dW, so clearly for the isothermal expansion or compression of a real gas where u = f(T) from the first law dU = 0 which means that the entire heat supplied is converted into work but from the second law of thermodynamics we find that in no process can the entire heat supplied can  be converted into work hence in reality some fraction of heat supplied is always used to increase the internal energy of the system.

According to Malus’s law Iαcos²θ, when θ=0^o or 180^o, I=I_ocos²0^o = I_o
i.e the intensity of the light transmitted by the analyser is maximum when the transmission axes of analyser and polarizer are parallel.

I₁ = n x -(e) x A x V
I₂ = n x 2e x A x V/4
   = n x e x A x V/2
Total Current = I₁ + I₂ 
=nea(V/2) - (-neav) (Since both ions will move in opposite directions,  we subtract them)
Hence Current I= (neav/2) + neav
                          = 3/2neaV
 

Given that λ = 200nm, d=700nm
θ = λ/d
We know that maximum angle can be 90⁰
No of rings that can be obtained say n,

If θ is so small then −

Icm = ma2/6
Now, applying parallel axis theorem
Ireq = Icm + m(a/√2)² 
Ireq = 2/3 ma² 

In the photoelectric effect, the work function is the minimum amount of energy (per photon) needed to eject an electron from the surface of a metal.Electrons ejected from a sodium metal surface were measured as an electric current.The minimum energy required to eject an electron from the surface is called the photoelectric work function.
This energy (work function) is a measure of how firmly a particular metal holds its electrons. The work function is important in applications involving electron emission from metals, as in photoelectric devices and cathode-ray tubes.

KEY CONCEPT : Magentic field at the centre of a circular coil of radius R carrying current i is 

Given : n ´ (2pr ') =2pR

⇒ nr '=R ...(1)

from (1) and (2), 

Explanation:the mean free path is the average distance traveled by a moving particle (such as an atom, a molecule, a photon) between successive impacts (collisions), which modify its direction or energy or other particle properties.

Let us consider an elemental length dl subtending an angle dθ at the centre of the circle. Let F_B be the magnetic force acting on this length. Then

F_B = BI (dl)  directed upwards as shown

= BI (Rdθ)              

Let T be the tension in the wire acting along both ends of the elemental length as shown. On resolving T, we find that the components. cancel out and
the components.  add up to balance FB.
At equilibrium  

Consider the surface facing upwards having points A, B, C and D in anticlockwise direction when viewing towards the surface from above. Let this be S
flux = S×B
As the flux increases, by Lenz's Law the induced current will be in the direction C B A D C, so as to oppose the increase in flux.

As at a corner, 8 cubes can be placed symmetrically, flux linked with each cube (due to a charge Q at the corner)
will be 

Now for the faces passing through the edge A, electric field E at a face will be parallel to area of face and so flux for these three faces will be zero. Now as the cube has six faces and flux linked with three faces (through A) is zero, so flux linked with remaining three faces will be 
Hence, electric flux passed through all the six faces of the cube is 

• The iron core of a transformer is made of Laminated silicon steel with special insulated coating to limit Eddy current loss.
• Electrical steel, also called lamination steel is specialty steel tailored to produce certain magnetic properties, such as a small hysteresis area (small energy dissipation per cycle, or low core loss) and high permeability.
  

Correct option is B.

KEY CONCEPT : When a charged particle is moving at right angles to the magnetic field then a force acts on it which behaves as a centripetal force and moves the particle in circular motion.