Solution

Iᵅ/Iᵦ=100
Rᴃ​=1000Ω
ꞵ=100
Vo=4 V
Vo/Vi=ꞵ(Rᶫ/Rᴃ)
Vi=4 x 1000/100 x 2000=0.02V= 20 mV

Solution

Moving coil galvanometer:
Principle : It works on the principle that a current carrying coil placed in a magnetic field experiences a torque.
Radial magnetic field: It is necessary to eliminate the effect of 0 on torque and hence enable us to make the scale of galvanometer linear.
Cylindrical soft iron core: It makes the magnetic lines of force pointing along the radii of the circle and also due to high permeability it intensifies the magnetic field and hence increases the sensitivity of the galvanometer.
Is=NBA/K or Q/I
where Q is the deflection of coil No, it can not be used to measure electric current because it is a highly current sensitive device which would show large deflection even with the passage of small current.
OR
(a) Self-inductance: The self inductance of a coil may be defined as the induced emf set up in the coil due to a unit rate of change of current through it.Its S.I. unit is Henry (H).

Solution

(b) According to lens maker’s formula,
1/f=(n-1)(1/R₁-1/R₂)
where f is the focal length, n is the refractive index and R₁ and R₂ is the radius of curvature of the lens.
Since, ng > np where g stands for glass and p stands for plastic. Therefore, we get (ng -1) > (np -1).
By lens maker’s formula, we know that focal length is inversely proportional to (μ -1).
Hence, fp > fg.
Thus, in the case of plastic lens, the thickness of the lens should be increased to keep the same focal length as that of the glass lens to give the same power.

Solution

Solution

(a) Unpolarised light : If the electric component of light vibrates in all the directions in the plane perpendicular to the direction of propagation, the light is known as unpolarised light.
Linearly polarised light: If the vibration of electric components of light is restricted in one direction only in the plane perpendicular to the propagation of light then light is known as linearly polarised light.
A polaroid consists of long-chain molecules aligned in a particular direction. The electric vectors along the direction of the aligned molecules get absorbed. So, when an unpolarised light falls on a polaroid, it lets only those of its electric vectors that are oscillating along a direction perpendicular to its aligned molecules to pass through it. The incident light thus gets linearly polarised.
(b)

Solution

Expression of Drift velocity: It is defined as the average velocity gained by the free electrons of a conductor in the opposite direction of the externally applied electric field. If an electron have initial velocity u1 and accelerated for time t1 then the velocity attained by it will be


Hence Ohm’s law is derived.
(b) The electric current will remain constant in the wire as it does not depend upon the cross-sectional area whereas the drift speed, current density, electric field depends upon the increasing area of cross-section with the following relations:

OR
(a) Kirchhoff’s laws:1. Kirchhoff’s first law or junction rule: In an electric circuit, the algebraic sum of currents at any junction is zero. i.e. ΣI= 0 . It is based on the conservation of charge.
2. Kirchhoff’s second law or loop rule: Around any closed loop of a network, the algebraic sum of changes in the potential must be zero. i.e. ΣΔV = 0 . It is based on the conservation of energy.