Match the parts of an analog moving-coil (PMMC) instrument to their functions. List I (Part) List II (Function) A. Former 1. Produces deflecting torque (in the magnetic field) B. Coil 2. Provides the base on which the coil is wound C. Core 3. Makes the magnetic field radial and uniform D. Spring 4. Provides controlling (restoring) torque

Introduction / Context:
PMMC (Permanent-Magnet Moving-Coil) instruments convert electrical quantities into mechanical deflection. Knowing what each mechanical part does is essential for understanding accuracy, damping, and scale linearity in measuring instruments used in electrical engineering labs.

Given Data / Assumptions:

• A PMMC meter has a light rectangular coil, a non-magnetic former, soft-iron core pieces that shape the field, and spiral hairsprings.
• The permanent magnet establishes the working magnetic field; interactions produce torque.
• We match four labeled parts to their correct roles.

Concept / Approach:

Deflecting torque is produced when a current-carrying coil sits in a magnetic field. A former is the mechanical support for the coil winding. Soft-iron pole pieces/core make the field radial so that the torque remains proportional to current for a linear scale. Spiral springs provide restoring (controlling) torque and also carry current to the moving coil.

Step-by-Step Solution:

Verification / Alternative check:

Linear scale behavior in PMMC instruments arises when the field is radial (core's function) and torque is proportional to coil current. The spring's opposing torque yields an equilibrium angle proportional to current, confirming the mapping.

Why Other Options Are Wrong:

• Pairing the former with deflecting torque confuses mechanical support with electromechanical action.
• Assigning the spring to produce deflection ignores its restoring role.
• Swapping core and spring roles contradicts meter construction theory.

Common Pitfalls:

Mixing up 'former' and 'core': the former holds the coil; the core shapes the field. Also forgetting that springs both control torque and provide electrical connections.

Final Answer:

A-2, B-1, C-3, D-4