# Errors in MI Type Instruments MCQ Quiz - Objective Question with Answer for Errors in MI Type Instruments - Download Free PDF

Last updated on Apr 16, 2024

## Top Errors in MI Type Instruments MCQ Objective Questions

#### Errors in MI Type Instruments Question 1:

The effect of stray magnetic fields on the actuating torque of a portable instrument is maximum when the operating field of the instrument and the stray fields are

1. Perpendicular
2. Parallel
3. Inclined at 60°
4. Inclined at 30°

Option 2 : Parallel

#### Errors in MI Type Instruments Question 1 Detailed Solution

Stray Magnetic Field:

• It is also called demagnetization fields.
• This is weak at full-scale deflection hence it can easily be distorted.
• Due to the external magnetic field inside, the operating field inside the meter is disturbed.
• This will lead to the weakness of the operating magnetic field.
• The stray magnetic field depends on the magnitude of the external magnetic field and its direction.
• When the magnitude of the external magnetic field is in phase with the main field, stray magnetic field error will be more.

This error is minimized by the following methods:

• By shielding the instrument with the help of a steel case.
• By sheet steel lining to the case.

In PMMC instrument permanent magnets are used. Therefore it will have a strong magnetic field.

In an MI instrument, the Air core is used. Therefore it will have a weak magnetic field.

The stray magnetic field error is more in the MI instrument compared to the PMMC instrument.

#### Errors in MI Type Instruments Question 2:

A moving iron instrument is calibrated with full scale deflection on 100 V DC. This instrument is used to measure 100 V at 50 Hz supply. Find the percentage error in reading if the instrument has a resistance of 2 kΩ and an inductance of 0.5 H

#### Errors in MI Type Instruments Question 2 Detailed Solution

Full scale deflection of instrument (VFSD) = 100V

Resistance (Rm) = 2 kΩ

Inductance (Lm) = 0.5 H

XL = 2πfL = 2π × 50 × 0.5 = 157.08 Ω

$${\rm{Full\;scale\;current}}\left( {{{\rm{I}}_{FSD}}} \right) = \frac{{100}}{{2 \times {{10}^3}}} = 50\;mA$$

Current through meter when 100 V at 50 Hz supply is applied

$$I = \frac{V}{Z} = \frac{{100}}{{\sqrt {{{\left( {2 \times {{10}^3}} \right)}^2} + {{\left( {157.08} \right)}^2}} }} = 49.84\;mA$$

$$Voltage\;reading\;of\;meter = \frac{{49.84}}{{50}} \times 100 = 99.68$$

$$\% \;error = \frac{{Measrued - true}}{{true}} \times 100 = \frac{{99.68 - 100}}{{100}} \times 100 = - 0.32\%$$
The text passage contains multiple questions related to errors in MI (Moving Iron) type instruments, including detailed solutions for one of the questions.
multiple_questions_with_answers
Given a text passage, determine:
    1. If it contains a mathematical question (including word problems or calculations)
    2. If an answer to that mathematical question is provided in the text

First, describe the content structure you found in 1-2 sentences.

Then provide your analysis in the following format:
TYPE: <one of the following values>
- NO_QUESTION
- SINGLE_QUESTION
- SINGLE_QUESTION_WITH_ANSWER
- MULTIPLE_QUESTIONS
- MULTIPLE_QUESTIONS_WITH_ANSWERS
system
# Errors in MI Type Instruments MCQ Quiz - Objective Question with Answer for Errors in MI Type Instruments - Download Free PDF

Last updated on Apr 16, 2024

## Top Errors in MI Type Instruments MCQ Objective Questions

#### Errors in MI Type Instruments Question 1:

The effect of stray magnetic fields on the actuating torque of a portable instrument is maximum when the operating field of the instrument and the stray fields are

1. Perpendicular
2. Parallel
3. Inclined at 60°
4. Inclined at 30°

Option 2 : Parallel

#### Errors in MI Type Instruments Question 1 Detailed Solution

Stray Magnetic Field:

• It is also called demagnetization fields.
• This is weak at full-scale deflection hence it can easily be distorted.
• Due to the external magnetic field inside, the operating field inside the meter is disturbed.
• This will lead to the weakness of the operating magnetic field.
• The stray magnetic field depends on the magnitude of the external magnetic field and its direction.
• When the magnitude of the external magnetic field is in phase with the main field, stray magnetic field error will be more.

This error is minimized by the following methods:

• By shielding the instrument with the help of a steel case.
• By sheet steel lining to the case.

In PMMC instrument permanent magnets are used. Therefore it will have a strong magnetic field.

In an MI instrument, the Air core is used. Therefore it will have a weak magnetic field.

The stray magnetic field error is more in the MI instrument compared to the PMMC instrument.

#### Errors in MI Type Instruments Question 2:

A moving iron instrument is calibrated with full scale deflection on 100 V DC. This instrument is used to measure 100 V at 50 Hz supply. Find the percentage error in reading if the instrument has a resistance of 2 kΩ and an inductance of 0.5 H

#### Errors in MI Type Instruments Question 2 Detailed Solution

Full scale deflection of instrument (VFSD) = 100V

Resistance (Rm) = 2 kΩ

Inductance (Lm) = 0.5 H

XL = 2πfL = 2π × 50 × 0.5 = 157.08 Ω

$${\rm{Full\;scale\;current}}\left( {{{\rm{I}}_{FSD}}} \right) = \frac{{100}}{{2 \times {{10}^3}}} = 50\;mA$$

Current through meter when 100 V at 50 Hz supply is applied

$$I = \frac{V}{Z} = \frac{{100}}{{\sqrt {{{\left( {2 \times {{10}^3}} \right)}^2} + {{\left( {157.08} \right)}^2}} }} = 49.84\;mA$$

$$Voltage\;reading\;of\;meter = \frac{{49.84}}{{50}} \times 100 = 99.68$$

$$\% \;error = \frac{{Measrued - true}}{{true}} \times 100 = \frac{{99.68 - 100}}{{100}} \times 100 = - 0.32\%$$
user
The text passage contains multiple questions related to errors in MI (Moving Iron) type instruments, including detailed solutions for one of the questions.

TYPE: MULTIPLE_QUESTIONS_WITH_ANSWERS