Assertion–Reason (connection choice for wattmeter on low-impedance loads): Decide the truth of the following statements. Assertion (A): For low-impedance loads, the wattmeter pressure (voltage) coil is connected directly across the load. Reason (R): A wattmeter measures apparent power.

Introduction / Context:There are two practical connection schemes for a dynamometer wattmeter—voltage coil on the load side or on the supply side of the current coil. The choice is made to minimize measurement error for particular load conditions.

Given Data / Assumptions:

• Low-impedance load implies high current and relatively low voltage drop across the load.
• The current coil has a small but non-negligible resistance causing a voltage drop.
• We seek to minimize errors due to including the current-coil drop in the measured voltage.

Concept / Approach:

For low-impedance (high-current) loads, connecting the pressure coil across the load avoids adding the current-coil voltage drop to the measured voltage. This reduces error. Separately, a wattmeter measures true power, not apparent power; its indication is P = V_rms * I_rms * cosφ, not V_rms * I_rms.

Step-by-Step Solution:

Verification / Alternative check:

Textbook connection rules: for low-impedance loads use “load-side” connection; for high-impedance/low-current loads the supply-side connection can be preferable to reduce current drawn by the pressure coil through the current coil branch.

Why Other Options Are Wrong:

• Any option implying R is true misstates the wattmeter function.
• Options making A false contradict standard practical guidance.

Common Pitfalls:

• Confusing real and apparent power; the wattmeter does not show V*A.
• Assuming one connection suits all loads; connection choice depends on load impedance.

Final Answer:

A is true R is false