Transformers Questions

• Transformer fundamentals — identifying input and output windings: In a conventional transformer used for power or signal isolation, which statement correctly identifies the typical roles of the windings?
• Transformer secondary current effect: If the number of turns on the secondary of an ideal transformer is increased (with the same primary drive and the same load impedance referred to its own side), what happens to the secondary current?
• Mutual inductance from coupling coefficient: Two coils have L1 = 75 mH and L2 = 105 mH with coefficient of coupling k = 0.45. What is the mutual inductance M between the coils?
• Impedance matching with an ideal transformer: What turns ratio (primary:secondary) is required to match a 1 kΩ source resistance to a 160 Ω load?
• Principle of mutual induction — key dependency: Mutual induction between two coils primarily depends on which factor in operation?
• Signal interfacing in RF and audio systems: A special transformer designed to convert an unbalanced (single-ended) signal to a balanced (differential) signal is called a:
• Maximum power transfer theorem in circuit design: Under what condition does a source deliver maximum power to a load (assume resistive source/load)?
• Ideal transformer power conservation: An ideal transformer has a 2:1 voltage ratio (primary:secondary) and delivers 100 W at the primary. What is the secondary power output?
• Transformer efficiency calculation: A 120 V rms primary draws 300 mA rms. The secondary supplies 18 V across a 10 Ω load. Compute the efficiency η = P_out / P_in.
• What does a transformer's turns ratio determine in practical circuits (assume linear operation)?
• Ideal transformer polarity — dot convention statement: In an ideal transformer, when the primary and secondary dotted terminals are taken as the positive reference ends, the secondary voltage is in phase with the primary voltage.
• Transformer power conservation (ideal case): With 100% efficiency (no losses), the power transferred to the secondary equals the power drawn from the primary, independent of step-up or step-down operation.
• Reflected load through a transformer — magnitude comparison: Is the equivalent (reflected) load seen at the primary always larger than the actual load connected to the secondary?
• Primary power vs. load change — behavior in an ideal transformer: If the load current on the secondary increases, does the real power drawn by the primary remain the same?
• Center-tapped secondary — phase relationship of the two half-windings: In a center-tapped transformer, the two secondary end-to-center-tap voltages have equal magnitude and are 180° out of phase with respect to the center tap.
• Open-circuit secondary — primary current behavior: If the secondary winding of a transformer is open-circuited, the primary current is nearly zero (only the small magnetizing current flows).
• Voltage–current trade in an ideal transformer: If the secondary voltage is stepped up by a certain ratio, the secondary current is stepped down by the same ratio (inverse of the turns ratio).
• Transformer basics — turns ratio check: A transformer has 700 turns on the primary winding and 35 turns on the secondary winding. Determine whether the stated turns ratio of 20:1 (primary:secondary) is correct, based on the definition turns ratio = Np:Ns.
• Condition for maximum power transfer — statement check: In a linear DC network, maximum power is transferred to the load when the load resistance equals the Thevenin (source) resistance seen from the load terminals. Evaluate this statement.
• Mutual inductance geometry — concept check: For mutual inductance to occur between two coils, must the coils be oriented at right angles to each other, or is coupling maximized when their magnetic axes are aligned?