Basic Electricity - Senior Secondary 1 - Moving iron instruments

TERM: 2^ND TERM

WEEK THREE

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:

Subject: BASIC ELECTRICITY

Topic: MOVING IRON INSTRUMENTS

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

I.) Define moving iron instruments

II.) Discuss the principles of operation of a moving iron instruments

III.) Mention  advantages of a moving iron instruments

IV.) Mention disadvantages of moving iron instruments

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures,

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

NOTE

MOVING IRON INSTRUMENTS

Moving iron instruments are types of measuring instruments that utilize the attraction or repulsion between a movable iron piece and a fixed magnetic field to measure various electrical quantities such as voltage, current, or power.

Principles of operation of moving iron instruments

1. Attraction and Repulsion: When an electric current flows through the coil of wire surrounding the iron piece, it creates a magnetic field. The iron piece, being ferromagnetic, experiences either attraction or repulsion depending on the polarity of the magnetic field. This movement of the iron piece is proportional to the electrical quantity being measured.
2. Deflection: The movement of the iron piece causes a mechanical deflection, which is then converted into a measurement reading on a calibrated scale. The degree of deflection corresponds to the magnitude of the electrical quantity being measured.

Advantages of moving iron instruments

1. Moving iron instruments can measure both AC and DC quantities over a wide range of values, making them versatile for various applications.
2. They are relatively robust and less susceptible to damage from mechanical shocks or vibrations compared to some other types of instruments.
3. Moving iron instruments are often more affordable than some other types of measuring instruments, making them accessible for general use.
4. They have a simple construction with fewer moving parts, leading to easier maintenance and calibration.
5. They can accurately measure non-linear loads, such as those found in electrical systems with reactive components.

Disadvantages of moving iron instruments

1. Moving iron instruments may not provide as high accuracy as some other types of instruments, particularly in comparison to more modern digital instruments.
2. They may exhibit hysteresis, meaning the indication may vary depending on whether the current is increasing or decreasing.
3. The performance of moving iron instruments can be affected by changes in temperature, leading to potential inaccuracies.
4. They may have a slower response time compared to some other types of instruments, especially in dynamic measurement situations.

EVALUATION: 1. What is a moving iron instruments?

2. Briefly discuss the principles of operation of a moving iron instruments
3. Mention 4 advantages of a moving iron instruments
4. Mention 3 disadvantages of a moving iron instruments

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively