Question

Two moving coil meters, M₁ and M₂ have the following particulars:
R₁ = 10 Ω, N₁ = 30,
A₁ = 3.6 × 10^–3 m², B₁ = 0.25 T
R₂ = 14 Ω, N2 = 42,
A₂ = 1.8 × 10^–3 m^2, B² = 0.50 T
(The spring constants are identical for the two meters).
Determine the ratio of (a) current sensitivity and (b) voltage sensitivity of M₂ and M₁.

Answer 1

For moving coil meter M₁:
Resistance, R₁ = 10 Ω
Number of turns, N₁ = 30
Area of cross-section, A₁ = 3.6 × 10^–3 m²
Magnetic field strength, B₁ = 0.25 T
Spring constant K₁ = K

For moving coil meter M₂:
Resistance, R₂ = 14 Ω
Number of turns, N₂ = 42
Area of cross-section, A₂ = 1.8 × 10^–3 m²
Magnetic field strength, B₂ = 0.50 T
Spring constant, K₂ = K

(b) Voltage sensitivity for M₂ is given as:
V_S2= (N₂B₂A₂) / (K₂R₂)