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:
Write formula: NI = N * I.Substitute values: 100 = 1000 * I.Compute: I = 100 / 1000 = 0.1 A.
Verification / Alternative check:
Scale reasoning: If 1000 turns produce 100 At at 0.1 A, then 1 A would give 1000 At; linear scaling confirms correctness.
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:
0.1 A
Discussion & Comments