Electro Magnetic Testing

8/13/2019 Electro Magnetic Testing

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potential difference

hysteresis

electrical resistance

impedance

7. Which symbol indicates specific conductivity?

J

s

IACS

8. The unit of specific conductivity is?

ohms/mm

mhos/cm

coulomb

milliampere

9. Which of the following is the reciprocal of specific conductivity?

specific voltage

specific gravity

specific inductance

specific resistivity

10. Calculate the magnetic flux density of a 100 ampere load flowing through a non magnetic conducto

having permeability of 4 p x 20 -7henry/meter at a distance of 0.03m from the conductor?

0.000666T

0.00125T

0.188T

150.7T

11. The following formula expresses ? / I = N ? / I =?

flux linkage

inductive reactance

self inductance

coil impedance

12. Mutual inductance is a term used to describe?

magnetic attraction of two elements in an electrical circuit

the effect of magnetic flux

the generation of current in one coil resultant from another coils flux linkage

the chain reaction of flux linkage

13. The RMS value of an alternating current sinusoidal wave form is calculated?

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Page 2 of 7Lavender International: Electro Magnetic Assessments: Module 10-1

9/19/2001http://www.lavender-ndt.com/assessments/et/module10-1.html


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multiplying peak by 1.43

dividing peak by 1.43

multipying peak by 0.707

dividing peak by 0.707

14. Which of the following statements are true?

inductive reactance is inversely proportional to frequency

inductive reactance is directly proportional to frequency

increased frequency reduces phase angle

increased resistance increases frequency

15. ? Lo is the notation which equates to?

Zo

2 p f L for a Loaded coil

Vo/I

2 p f L for a coil in the air

16. Normalisation of a complex plane impedance diagram is achieved by?

dividing the resistive value by reactive value

multiplying 2 p f L R

R - Ro / ? Lo

dividing the inductive reactance of an unloaded air coil into the loaded values of 2 p f

L and R

17. The impedance phasor, Z, lies at an angle ? derived by?

multiplying the inductive reactance by 0.707dividing resistance by ? L

multiplying TAN ? by XL

dividing L by R to achieve TAN ?

18. Angular frequency in radians per second is defined as a function of?

2 p f

2 p / T

a - p / 2

2 p / T and a - p / 2

2 p f and

19. How many radial degrees is one radian?

14.32

28.64

57.29

114.59

20. Complex number calculations for impedance plane diagrams contain which of the following number

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types?

real numbers

imagninary numbers

logrithmic numbers

real and imaginary numbers

All of the above

21. Calculate the phase angle given that the probe frequency is 60Hz, the inductance if 20 Henries andcoil resistance is 530 ohms?

14.2 degrees

85.9 degrees

49.2 degrees

23.5 degrees

22. Which of the following transducer types are available in electromagnetic inspection?

feed through

encircling

forked

all the above

only feed through and encircling

23. Calculate the standard depth of penetration at a test frequency of 50KHz, ? resistivity in micro ohmcentimetres = 41.7, r=1?

1.4mm

14mm

0.14mm2.8mm

24. Calculate the fill factor for a 30mm diameter coil on a 27mm diameter copper bar?

0.063

0.81

0.90

1.11

25. Which of the following variables could be used to measure none conductivity coating thicknesses?

fill factor

edge effect

lift off

all the above

fill factor and lift off only

26. Lift off is maintained at a constant level?

to avoid probe contamination

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33. When using surface coils on small diamater tube what disadvantages may be encountered?

reduced speed of inspection

reduced sensitivity

increased resolution

all the above

34. In modulation analysis why are filters used?

reduce signal to noise ratio

reduce effects of small changes in conductivity

amplify the response from cracks

seperate edge effect from lift off

35. When trying to locate cracks in a bar that has a minimum length of 10mm which of the following coilsizes would achieve the best results?

25mm

20mm

15mm

10mm

36. Of the following which will greatly affect the conductivity of a material?

coil diameter

material thickness

material temperature

material diameter

37. Which of the following are expressions used in electromagnetic inspection?

algebraic function

imaginary numbers

exponential functions

all the above

38. The impedance of an empty coil would ??? as an operating frequency decrease?

increase

remain the same

decrease

frequency has no effect on coil impedance

> Check Your Answers

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Lavender International, Unit 7, Penistone Station, Sheffield, S36 6HP , United Kingdom




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Here are the corrections:

1. any of the above2. automated mass inspection of similar parts at high rates3. any of the above

4. any of the above5. current6. electrical resistance

7. s8. mhos/cm

9. specific resistivity10. 0.000666T11. self inductance

12. the generation of current in one coil resultant from another coils flux linkage13. multipying peak by 0.707

14. inductive reactance is directly proportional to frequency

15. 2 p f L for a coil in the air16. dividing the inductive reactance of an unloaded air coil into the loaded values of 2 p f

L and R17. dividing L by R to achieve TAN ?

18. 2 p f and19. 57.2920. All of the above

21. 85.9 degrees22. all the above

23. 1.4mm24. 0.81

25. lift off26. to reduce non relevant output signals27. skin efect

28. change in part temperature29. shape the field and shield test coil with magnetic material30. lift off errors

31. stainless steel32. an absolute coil and a differential coil

33. reduced speed of inspection34. reduce effects of small changes in conductivity35. 10mm

36. material temperature37. all the above

38. decrease

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Electro Magnetic Testing