Moving iron instrument can be used for the measurement of:

Explanation:

Moving Iron Instrument

Definition: A moving iron instrument is an electrical measurement device used to measure both alternating current (AC) and direct current (DC). It operates on the principle of electromagnetic force, where a piece of iron moves in response to the magnetic field produced by the current flowing through a coil.

Working Principle: The moving iron instrument consists of a coil and a piece of soft iron. When current flows through the coil, it generates a magnetic field. The magnetic field induces a force on the iron piece, causing it to move. The movement is proportional to the strength of the current, and this movement is indicated on a calibrated scale. There are two main types of moving iron instruments: attraction type and repulsion type.

Attraction Type: In this type, the iron piece is attracted towards the coil when current flows through it. The movement of the iron is proportional to the square of the current.

Repulsion Type: In this type, two pieces of iron are placed such that when current flows through the coil, both pieces are magnetized with the same polarity and repel each other. The repulsion causes a movement that is also proportional to the square of the current.

Advantages:

• Can measure both AC and DC currents accurately.
• Rugged and robust construction, making them durable and suitable for industrial environments.
• Relatively simple design and low cost.

Disadvantages:

• Non-linear scale, especially at the lower end, due to the square law response.
• Less sensitive compared to moving coil instruments.
• Prone to errors due to hysteresis and eddy currents in the iron parts.

Applications: Moving iron instruments are commonly used in industrial and laboratory settings for measuring AC and DC currents and voltages. They are particularly useful in applications where ruggedness and the ability to measure both types of currents are required.

Correct Option Analysis:

The correct option is:

Option 2: AC as well as DC current.

This option correctly describes the capability of moving iron instruments. They are designed to measure both alternating and direct currents, which is a significant advantage in various practical applications. The iron piece in the instrument responds to the magnetic field generated by the current, whether it is AC or DC.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: Only AC current.

This option is incorrect because moving iron instruments can measure both AC and DC currents. While they are effective for AC measurements due to their ability to respond to the magnetic field generated by the alternating current, they are equally capable of measuring DC current.

Option 3: Only DC current.

This option is also incorrect because it limits the functionality of moving iron instruments to DC measurement only. As previously explained, these instruments can measure both AC and DC currents due to their design and operational principle.

Option 4: Only heat.

This option is entirely incorrect as moving iron instruments are designed to measure electrical current, not heat. The instrument operates based on the electromagnetic force exerted on the iron piece by the magnetic field of the current, and heat measurement is not within its scope of functionality.

Conclusion:

Understanding the operational principles and capabilities of moving iron instruments is crucial for their effective application. These instruments offer the versatility to measure both AC and DC currents, making them valuable tools in various electrical measurement scenarios. Their rugged design and ability to handle different types of current flow enhance their utility in industrial and laboratory environments, despite some limitations such as non-linearity and sensitivity issues.