SOLUTION

Ammeter and Voltmeter connection in DC power measurement introduces a systematic error, generally referred to as insertion error.

Insertion errors:- These are errors that result from the insertion of the instrument into the position to measure a quantity affecting its value. For example, inserting an ammeter into a circuit to measure the current will change the value of the current due to the ammeter’s own resistance.

In the Ammeter in front of the voltmeter connection as shown in the fig. the ammeter measures the current flowing into the voltmeter, I_L, as well as that flowing into the load, I_V.

In ammeter Behind the voltmeter connection, the voltmeter measures the voltage drop across the load, VL, in addition to that dropping across the ammeter, VA. So both connections give an excess of measured power, representing the power absorbed by the instrument connected closer to the load.