In connecting head telephones directly in...

🔍 Key Concepts

• Vacuum tube plate circuit – understand what the plate (anode) does and how current flows through the tube and the load (headphones) • Permanent magnet headphones – how the magnetic field from the current in the coil interacts with the field of the permanent magnet • Polarity and sensitivity – when and why the direction of current through a magnetic coil affects efficiency or sensitivity

💭 Think About

• Think about whether headphones will still produce sound if current flows in either direction through the coil, and whether one direction is more efficient than the other • Ask yourself what happens if the magnetic field from the coil helps (aids) the permanent magnet versus when it opposes it • Consider whether “maximum sensitivity” and “current opposed to the permanent magnet field” can both be true at the same time

✅ Before You Answer

• Verify whether dynamic or magnetic headphones care about the direction of DC current for how strongly they respond • Check whether “opposing the permanent magnet field” would tend to weaken or strengthen the total magnetic field in the headphone gap • Decide if both statements (A and B) can logically be correct together, or if one of them must be wrong based on basic magnetism (fields adding vs. cancelling)

In connecting head telephones directly in the plate circuit of a vacuum tube one should observe the proper polarity:

To maintain maximum sensitivity in the headphones

So its current flows opposed to the field strength of the permanent magnet

A & B

None of the above

🔍 Key Concepts

💭 Think About

✅ Before You Answer