What causes a voltage to appear across the secondary winding of a transformer when an AC voltage source is connected across its primary winding?
The correct answer is C: Mutual inductance. What causes a voltage to appear across the secondary winding of a transformer when an AC voltage source is connected across its primary winding is mutual inductance. The changing magnetic field from the primary induces voltage in the secondary through mutual inductance. For amateur radio operators, this is how transformers work. Understanding this helps when using transformers.
Exam Tip
Transformer voltage transfer = mutual inductance. Think 'T'ransformer = 'T'ransfers through 'M'utual 'I'nductance. Changing magnetic field from primary induces voltage in secondary through mutual inductance. Not capacitive coupling, not displacement current, not mutual capacitance - just mutual inductance.
Memory Aid
"Transformer voltage transfer = mutual inductance. Think 'T'ransformer = 'T'ransfers through 'M'utual 'I'nductance. Changing magnetic field from primary induces voltage in secondary through mutual inductance. How transformers work."
Real-World Application
You connect AC voltage to a transformer's primary winding. The changing current creates a changing magnetic field. This magnetic field links to the secondary winding through mutual inductance, inducing voltage in the secondary. This is how transformers transfer energy - through mutual inductance, not through direct electrical connection.
Key Concepts
Why Other Options Are Wrong
Option A (Capacitive coupling): Incorrect. Transformers don't work through capacitive coupling - they work through magnetic coupling (mutual inductance). Capacitive coupling is different.
Option B (Displacement current coupling): Incorrect. Transformers don't work through displacement current - they work through mutual inductance. Displacement current is a different concept.
Option D (Mutual capacitance): Incorrect. Transformers don't work through mutual capacitance - they work through mutual inductance. Mutual capacitance is different.
题目解析
The correct answer is C: Mutual inductance. What causes a voltage to appear across the secondary winding of a transformer when an AC voltage source is connected across its primary winding is mutual inductance. The changing magnetic field from the primary induces voltage in the secondary through mutual inductance. For amateur radio operators, this is how transformers work. Understanding this helps when using transformers.
考试技巧
Transformer voltage transfer = mutual inductance. Think 'T'ransformer = 'T'ransfers through 'M'utual 'I'nductance. Changing magnetic field from primary induces voltage in secondary through mutual inductance. Not capacitive coupling, not displacement current, not mutual capacitance - just mutual inductance.
记忆口诀
Transformer voltage transfer = mutual inductance. Think 'T'ransformer = 'T'ransfers through 'M'utual 'I'nductance. Changing magnetic field from primary induces voltage in secondary through mutual inductance. How transformers work.
实际应用示例
You connect AC voltage to a transformer's primary winding. The changing current creates a changing magnetic field. This magnetic field links to the secondary winding through mutual inductance, inducing voltage in the secondary. This is how transformers transfer energy - through mutual inductance, not through direct electrical connection.
错误选项分析
Option A (Capacitive coupling): Incorrect. Transformers don't work through capacitive coupling - they work through magnetic coupling (mutual inductance). Capacitive coupling is different. Option B (Displacement current coupling): Incorrect. Transformers don't work through displacement current - they work through mutual inductance. Displacement current is a different concept. Option D (Mutual capacitance): Incorrect. Transformers don't work through mutual capacitance - they work through mutual inductance. Mutual capacitance is different.
知识点
Transformer, Mutual inductance, Primary and secondary, Magnetic coupling
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.