Question

Assertion : In an ideal step-down transformer, the electrical energy is not lost.

Reason (R): In a step-down transformer, voltage decreases but the current increases.

• A. If both Assertion and Reason (R) are true and Reason (R) is the correct explanation of Assertion .
• B. If both Assertion and Reason (R) are true but Reason (R) is not the correct explanation of Assertion .
• C. If Assertion is true but Reason (R) is false.
• D. If both Assertion and Reason (R) are false.

Hint:

In an ideal transformer, energy conservation occurs without losses, even when voltage and current change.

Answer 1

The Correct Option is B

In an ideal step-down transformer, electrical energy is conserved, meaning input power equals output power:

P_input = P_output

Where:

P_input = V_primary × I_primary

P_output = V_secondary × I_secondary

For a step-down transformer, the primary voltage (V_primary) exceeds the secondary voltage (V_secondary), while the secondary current (I_secondary) is greater than the primary current (I_primary). This is expressed as:

V_primary > V_secondary

I_secondary > I_primary

This illustrates that in an ideal step-down transformer, voltage decreases as current increases, maintaining power conservation. This supports the truth of Reason (R). However, Reason (R), which attributes the power maintenance to current increase from voltage decrease, does not directly explain the Assertion that electrical energy is not lost. The absence of energy loss is attributable to the ideal assumption (i.e., zero resistive/inductive losses), not the voltage and current transformations.

Therefore, both the Assertion and Reason (R) are true, but Reason (R) does not correctly explain the Assertion.