An electromagnet has 1000 turns (N = 1000). What current is required to produce an mmf of 100 ampere-turns (NI = 100 At)?

Introduction / Context:Magnetomotive force (mmf) quantifies the 'driving force' for magnetic flux in a magnetic circuit, analogous to emf in electrical circuits. The basic relation is mmf = N * I (ampere-turns). This question reinforces direct proportionality among mmf, turns, and current.

Given Data / Assumptions:

• Number of turns N = 1000.
• Required mmf NI = 100 ampere-turns.
• Core properties and reluctance are irrelevant for computing current from mmf.

Concept / Approach:

• Use mmf formula: NI = N * I.
• Solve for I: I = NI / N.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

• 10 A and 100 A: Would produce 10,000 At and 100,000 At respectively, far above 100 At.
• 1000 A: Physically unrealistic for small coils; would give 1,000,000 At.
• None of the above: Incorrect because 0.1 A satisfies the requirement.

Common Pitfalls:

• Confusing ampere-turns with amperes; mmf depends on both current and turns.
• Overlooking simple division when rearranging NI = N * I.

Final Answer: