Moving Charges and Magnetism Flashcards
(26 cards)
What is the SI unit and dimensions of a magnetic field?
The SI unit of a magnetic field is tesla (T) of Weber/meter (wb/m²) or N/A¹m¹ and its CGS unit is gauss. (1 telsa = 10⁴ gauss)
Dimensions: [M/T²A¹]
What is Bio Savart’s Law?
According to Bio Savarts law,
dB ∝ Idlsinθ/r²
dB = μₒ/4π . Idlsinθ/r²
μₒ = 4π x 10⁻⁷
In terms of magnetizing force,
dH = 1/4π . Idlsinθ/r²
What are the features of Bio-savart’s law?
- The law is analogous to Coulomb’s law in electrostatics.
- The direction of dB is perpendicular to Idl and r. It is given by the right-hand thumb rule.
- If θ = 0 then no current passes through the conductor.
- If θ = 90 then the current on the conductor is maximum.
What is Electric Permittivity?
The physical quantity which determines the degree of interaction of the electric field with the medium.
What is Magnetic Permittivity?
The physical quantity that measures the ability of a substance to acquire magnetism in a magnetic field.
The relation between Eₒ and is μₒ?
Eₒμₒ = 1/c²
What is the magnetic field of a current-carrying conductor?
Magnetic field for a straight wire of finite length,
B = μₒI/4πR (sinα + sinβ)
Magnetic field for a straight wire of infinite length,
B = μₒI/2πR
What is the magnetic field on the axis of a current-carrying circular loop?
B = μₒIa²/2(r² + a²)³’²
and for N turns,
B = μₒNIa²/2(r² + a²)³’²
What is the magnetic field in the center of the current carrying loop?
The magnetic field at its center C is given by,
B = μₒNI/2R
What is Ampere’s Circutial Law?
The line integral of a magnetic field B around any closed path in a vacuum is times the net current I enclosed by the curve.
∫B.dl = μₒIₙₜ
What is the magnitude of a magnetic field of a long straight thin wire using Ampere’s law?
B = μₒI/2πr
What is the magnetic field due to an infinitely long current carrying straight wire?
When P is lying outside the wire,
r > R
B = μₒI/2πr
When P is lying on the surface of the wire,
r = R
B = μₒI/2πR
When P is lying inside of the wire,
r < R
Either the current will be B = 0
Or B = μₒIr/2πR²
What is a solenoid?
A solenoid is an insulated long wire closely wound in the form of a helix. Its length is very long compared to its diameter.
What is the magnetic field of a Solenoid?
B = μₒnI
B = 1/2μₒnI
What is the force on a moving charge particle in a uniform magnetic field?
F = q(v x B)
F = q[E + (v x B)]
What is the motion of a moving charged particle in a uniform magnetic field?
The motion of the particle in a plane perpendicular to B is as before a circular one, thereby producing a helical motion.
What is the radius (in terms of kinetic energy), time period, angular frequency, frequency, and Angular speed of a moving charged particle in uniform magnetic field in terms of?
r (radius) = √2mK/qB
T (time period) = 2πm/qB
v (frequency) = Bq/2πm
w (angular frequency) = 2π/T = Bq/m
w (angular speed) = v/r = (qB)/m
What is the force on a current-carrying conductor placed in a uniform magnetic field?
F = I B L sinθ or i(L x B)
What is the force between two parallel current-carrying conductors?
F = μₒ/4π. 4I₁I₂/r
Torque experienced by a current loop in a uniform magnetic field?
τ = MBsinθn = M x B
as M = NIA
τ = BINAsinθ
What is the Galvanometer constant?
G = k/NBA
What is the Current Sensitivity?
The current sensitivity of the galvanometer is the deflection produced per unit of current flowing through it.
I = NAB/k
What is the Voltage Sensitivity?
Voltage sensitivity is the deflection per unit voltage.
V = [NAB/k]I/V or NAB/kR
What is the conversion of a galvanometer into an Ammeter?
S = [Iᵥ/I - Iᵥ] G
or
Rₚ = GS/G+S
