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Difficulty: MediumMagnetic Force and Electromagnetism

Match each electromagnetic device or component listed on the left with its corresponding function or operating principle on the right.

  • Moving coil galvanometerDetects and measures tiny electric currents using the torque produced by magnetic force on a current-carrying loop
  • Electric motorConverts electrical energy into mechanical rotational energy via magnetic forces on a current-carrying conductor
  • Split-ring commutatorReverses current direction in the armature coil every half-rotation to ensure continuous rotation in one direction
  • Soft iron coreConcentrates magnetic flux lines to produce a strong and radial magnetic field

Answer

Moving coil galvanometer matches with detecting/measuring small currents via torque; Electric motor matches with converting electrical energy to mechanical energy; Split-ring commutator matches with reversing current every half-cycle to maintain continuous rotation; Soft iron core matches with concentrating magnetic flux to create a radial magnetic field.
Each electromagnetic device or component relies on magnetic forces: moving coil galvanometers convert current to proportional coil torque; electric motors convert electrical energy into continuous mechanical rotation; split-ring commutators reverse current every half-turn to keep torque unidirectionally directed; soft iron cores concentrate magnetic flux to establish strong radial fields.

Step-by-Step Solution

1
Identify the primary operational application of the moving coil galvanometer.
It detects small currents using the torque T=NIABsin⁡θT = NIAB \sin\theta exerted on a current-carrying coil in a magnetic field.
This establishes the link between galvanic deflection and electrical current measurement.
2
Identify the energy transformation principle of an electric motor.
The motor converts input electrical power into mechanical torque via magnetic force F=BILsin⁡θF = BIL\sin\theta.
This connects the motor to its fundamental mechanical output function.
3
Analyze the mechanical role of a split-ring commutator in DC devices.
It alternates current flow directions in the loop every 180∘180^\circ.
Without reversals, the coil would oscillate around equilibrium instead of continuously rotating.
4
Determine the ferromagnetic enhancement provided by a soft iron core.
It increases field strength and maintains a radial field orientation.
High magnetic permeability concentrates magnetic field lines effectively.

Key Concept

Operating principles and structural functions of electromagnetic devices based on magnetic torque and forces
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Topics

Magnetic Force and Electromagnetism

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