The D'Arsonval- movement can be converted into audio frequency ac ammeter by adding aThermocoupleTransducerChopperRectifierNone of the above

To tackle the question about converting a D'Arsonval movement into an audio frequency AC ammeter, let's break down the potential options provided:

1. Thermocouple: This device is primarily used for measuring temperature. It generates a voltage based on temperature differences, which wouldn't be appropriate for an ammeter.

2. Transducer: While transducers can convert energy from one form to another, they do not directly provide a solution for converting a D'Arsonval meter into an AC ammeter specifically.

3. Chopper: A chopper can switch the DC input to a D'Arsonval movement, allowing it to interpret varying AC currents. This makes it a suitable choice for conversion.

4. Rectifier: A rectifier converts AC to DC, which is useful, but it does not directly modify the D'Arsonval movement itself for use as an AC ammeter.

Given these explanations, the most appropriate option for converting a D'Arsonval movement into an audio frequency AC ammeter is:

Final Answer

Chopper