A vibration magnetometer placed in magneticmeridian has a small bar ma...
Given:
Time period of oscillation in earth's magnetic field, T₁ = 2 s
Horizontal magnetic field of earth, B₁ = 24 µT
Horizontal magnetic field produced by current carrying wire, B₂ = 18 µT
To find:
New time period of oscillation, T₂
Solution:
Angular frequency of oscillation in earth's magnetic field, ω₁ = 2π/T₁
Magnetic moment of the small bar magnet, m = BAN
where B is the magnetic field, A is the area of cross-section of the magnet and N is the number of turns.
When the magnet is displaced by an angle θ from its equilibrium position, the restoring torque on the magnet is given by τ = mBsinθ
The equation of motion of the magnet is given by I(d²θ/dt²) + τ = 0
where I is the moment of inertia of the magnet.
On substituting the values, we get:
I(d²θ/dt²) + mBsinθ = 0
d²θ/dt² + (mB/I)sinθ = 0
This is a non-linear differential equation and its solution can be obtained by assuming the small angle approximation, sinθ ≈ θ.
On substituting this approximation, we get:
d²θ/dt² + (mB/I)θ = 0
This is a simple harmonic differential equation and its solution is given by:
θ = θ₀cos(ωt)
where θ₀ is the amplitude of oscillation and ω = √(mB/I) is the angular frequency of oscillation.
The time period of oscillation is given by:
T = 2π/ω
For the magnetic field produced by the current carrying wire, the new angular frequency of oscillation is given by:
ω₂ = √(m(B₁ - B₂)/I)
The new time period of oscillation is given by:
T₂ = 2π/ω₂
On substituting the values, we get:
T₂ = 4 s
Therefore, the new time period of oscillation is 4 s.