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 conservation is maintained, meaning that the input power is equal to the output power, mathematically represented as:

P_input = P_output

Where,

P_input = V_primary × I_primary

P_output = V_secondary × I_secondary

In a step-down transformer, the primary voltage (V_primary) is higher than the secondary voltage (V_secondary), but the current in the secondary (I_secondary) is higher than in the primary (I_primary). Mathematically, it can be shown as:

V_primary > V_secondary

I_secondary > I_primary

This demonstrates that in an ideal step-down transformer, while the voltage decreases, the current increases to maintain power, supporting the statement that the Reason (R) is true. However, the Reason (R) being the increase in current due to a decrease in voltage does not directly explain the Assertion that electrical energy is not lost. The lack of energy loss is due to the ideality assumption (i.e., no resistive/inductive losses), not the changes in voltage and current. Therefore,

If both Assertion and Reason (R) are true but Reason (R) is not the correct explanation of Assertion.