Question

a pmmc mechanism having ifsd of 20 ma and internal resistance of 2kohm is used for measuring a current of 2a. Calculate value of shunt required​

Answer 1

Answer:

Concept:

PMMC torque equation

Td = Tc

Td = deflecting torque

Td = BINA

where B = flux density

I = current in moving coil

N = number of turns of the coil

A = effective Area of coil

Tc = controlling torque

Tc = Kθ

K = spring constant

θ = deflection Angle.

Kθ = BINA

Calculation:

Given:

θ = 100°, N = 60, B = 0.5T, l = 25mm, W = 18 mm

Area (A) = l × W = 25 × 18 = 450 mm2 = 450 × 10-6 m2

K = 1.5 × 10-6 N-m/degree

By torque equation

Kθ = BINA

1.5 × 10-6 × 100 = 0.5 × I × 60 × 450 × 10-6

I = 11.11 mA

Answer 2

Answer:

The Ammeter is a measuring instrument used to find the strength of current flowing around an electrical circuit when connected in series with the part of the circuit being measured