electrical easa 2

8/11/2019 Electrical Easa 2

1/17

1. What is the phase different across resistor and applied voltage in pure resistance circuit?

a) 40

b) 90

c) 0

Correct Answer : 0

Explanation.

2. In an RC circuit, the component voltages UR=30 VAC and UC=40Vac are measured with a

multimeter. What is the total voltage UAC to which the series circuit is connected?

a) 30 VAC

b) 50 VAC

c) 70 VAC

Correct Answer : 50

Explanation. 2+ UC2

302+ 402

2500 = 50VAC


2/17

3. What is the time constant (tau) of the circuit?

a) 10 sec

b) 1 sec

c) 2sec

Correct Answer : 1 sec

Explanation. = R . C

= 0.5 x (2x 10-6

)

= 1 x 10-6

= 1 sec

4. An inductor of 1 mH is applied to a 100 Hz sinusoidal source. What is the inductive reactance of

circuit? (XL= 2 x x f x c)

a) XL= 0.628 Ohm

b) XL= 1 Ohm

c) XL= 100 Ohm

Correct Answer : XL= 0.628 Ohm

Explanation XL= 2 x x100 x (1x10-3)

= XL= 0.628 Ohm

10 V2 F

0.5


3/17

5. What is retentivity?

a) The amount of magnetic field strength, necessary to saturate a ferromagnetic material

b) The capability of a material to retain magnetism for a long period of time

c) The ratio of remanence versus coercitive force

Correct Answer : The capability of a material to retain magnetism for a long period of time

Explanation. 3.10.1HO - 8

6. Which of the shown circuits is given in the pointer diagram?

a) Circuit A

b) Circuit B

c) Circuit C

A B C

Correct Answer : Circuit C

IR

XL

U

I


4/17

7. Two coils with a induction of 60 H are connected in parallel. What is the total inductance of this

circuit?

a) 120 H

b) 30 H

c) 60 H

Correct Answer : 30 H

Explanation. LT= L1X L2 OR L = 60 = 30 H

L1+ L2 2 2

8. The process whereby the magnetism has been led or induced in the iron or steel is known as

a) Magnetism

b) Electro magnetism

c) Induction

Correct Answer : Induction

Explanation. 3.10.1HO1

3.10.1.3 Magnetization

- Process is called induction; meaning that magnetism has been transferred into the

iron, or induced

9. A circuit is consisting of four 500 Ohm resistors in parallel. What is the total resistance Rt?

a) 125 Ohm

b) 250 Ohm

c) 500 Ohm

Correct Answer : 125 Ohm

Explanation. RT= 500 = 125 Ohm

4


5/17

10) What is the usual application for a wire wound resistor

a) General purpose application

b) High power application for electric circuits

c) Low power application for electronic circuits

Correct Answer : High power application for electric circuits


11. What is a rheostat?

a) A rheostat is a device that delivers adjustable capacitance

b) A rheostat is a device that delivers adjustable inductance

c) A rheostat is a device that delivers adjustable resistance

Correct Answer : A rheostat is a device that delivers adjustable resistance


12. How much turns must have the primary winding of the shown transformator

a) 18

b) 220

c) 440

Correct Answer : 440

Explanation UP = NP

US NS

220 = NP

18 36

NP = 440

I136 W dg

X1 X2 18 v220 v


6/17

13. Which of the following is the formula giving the relationship between voltage and the number of

turns in a transformer?

a) UP = NP

US NS

b) UP = NS

US NP

c) US = NP

UP NS

Correct Answer : UP = NPUS NS

Explanation 3.15.2HO -1

14. When magnetic field strength is increased, it will a eventually reach a _____________ point

a) Remanance

b) Coercive

c) Saturation

Correct Answer : Saturation

15. Which statement about ferromagnetic material is correct?

a) Ferromagnetic material can be soft or hard magnet material

b) Ferromagnetic material is always permanent magnetic material

c) The permeability of ferromagnetic material is less than 1

Correct Answer : Ferromagnetic material can be soft or hard magnet material

Explanation 3.10.1HO8


7/17

16. What is the difference between an air-coil and ferrite core coil?(both coils are supplied with the

same DC-voltage)

a) The current through the ferrite core coil is higher

b) The direction of the magnetic flux in both coils is opposite

c) The ferrite core coil developers a higher magnetic a higher magnetic flu density

Correct Answer : The current through the ferrite core coil is higher

17. What happens to the inductance if the numbers of turns on a core are doubled?

a) It decrease by a factor of four

b) It increase by a factor of four

c) It increase by factor of two

Correct Answer : It increase by a factor of four

Explanation


8/17

18. There is a current in a conductor. Which is the correct rule to detect the direction of fluxlines

around a conductor?

a) Corkscrew rule

b) Counter-clockwise-rule

c) Left-hand-rule

Correct Answer : Corkscrew rule

Explanation 3.10.1HO4 (The Magnetic Effect of Current)

19. Which of the rules is the correct one, to detect the direction of current of a generator?

a) Corkscrew rule

b) Left-hand-rule

c) Right-hand-rule

Correct Answer : Right-hand-rule

20. How is the direction of magnetic field-lines inside a permanent magnet?

a) From the north pole to the south pole

b) From the south pole to the north pole

c) There are no magnetic field-lines inside a magnet. Magnet field-lines are only outside

permanent magnet

Correct Answer : From the south pole to the north pole

Explanation 3.10.1HO (Magnetic Field of Permanent Magnets)

21. What is reluctance in a magnetic circuit?

a) The description for magnetic circuit

b) The description for magnetic resistance

c) The electrical resistance of an electromagnetic

Correct Answer : The description for magnetic resistance


9/17

22. What happens when a relay is energized?

a) All relay contacts close

b) An air gap is formed in the relays magnetic circuit between the armature and the core

c) The magnetic core flux-attracts the armature

Correct Answer : The magnetic core flux-attracts the armature

23. Which of the following answers contains only parameters, shown in a hysteresis loop for a

ferromagnetic material?

a) The electric current and voltage as well as the magnetic romanence

b) The electric current and voltage as well as the magnetic romanence and coercive force

c) The magnetic field strength, magnetic flux density, remanence and coercive force

Correct Answer : The magnetic field strength, magnetic flux density, remanence and coercive force

24. When switching off the supply, the back EMF in a collapsing field in a inductor...

a) Can be multiple times than the forward EMF

b) Is equal to forward EMF

c) Never exceeds forward EMF

Correct Answer : Can be multiple times than the forward EMF

25. What is the permeability value of air

a) 0

b) 1

c) 100

Correct Answer : 1

Explanation 3.9.1HO -4

26. What formula is used for average value?

a) 0.637 x Peak Value

b) 0.673 x Peak Value

c) 0.367 x Peak Value

Correct Answer :0.637 x Peak Value


10/17

27. Convert 10v RMS to Peak Value

a) 14.14 Volts

b) 6.37 Volts

c) 7.07 Volts

Correct Answer : 14.14 Volts

Explanation : Peak Value = RMS x 1.414

= 10 x 1.414 = 14.14

28. For a Peak Value of 100v, the RMS is

a) 0.707 Volts

b) 70.7 Volts

c) 7.07 Volts

Correct Answer : 70.7 Volts

Explanation : RMS = Peak Value x 0.707

= 100 x 0.707 = 70.7

29. The Peak Value of sinusoidal waveform can be calculated by multiplying the RMS value by

a) 0.707

b) 1.41

c) 1.732

Correct Answer : 1.41

Explanation : Peak Value = RMS x 1.414


11/17

30. What is the peak-to-peak value of an alternating current?

a) The average value of two peaks of the waveform

b) The RMS value times two ( 0.707 x 2)

c) The value between the maximum in a positive direction and the maximum value of a

negative direction of an AC waveform

Correct Answer : The value between the maximum in a positive direction and the maximum value

of a negative direction of an AC waveform

Explanation :


12/17

31. Determine the resistor Rx within this circuit, when the motor reads zero

100

1000 159

a) Rx = 10 Ohm

b) Rx= 15.9 Ohm

c) Rx= 6.3 Ohm

Correct Answer : Rx= 15.9 Ohm

Explanation : 3.7.1HO5 / 3.7.1HO6

32. What is the disadvantage of a rotating armature type alternator compared to a rotating field

type?

a) Slip rings are not used

b) Spark occurs on the brush and slip rings

c) No arcing at the slip rings

Correct Answer : Spark occurs on the brush and slip rings

33. How much is the induced voltage at 90o

at rotating conductor?

a) Maximum

b) Minimum

c) Zero

Correct Answer : Maximum

R2 R3

RxR1


13/17

34. What happens to a conductor free to move in a magnetic field, when a current is following

through it?

a) The conductor starts moving (Lorentz force Law)

b) The current flow decreases to zero

c) The resistance of the conductor decrease (ntc)

Correct Answer : The conductor starts moving (Lorentz force Law)

35. Define Slip

a) Difference between stator field speed and supply voltage

b) Difference between stator field speed and rotor field

c) Difference between stator field speed and rotor speed

Correct Answer : Difference between stator field speed and rotor speed

Explanation : 3.18.1HO2

36. What is the purpose of capacitor in the single phase AC motor?

a) To cause the current in the start winding lagging

b) To cause the voltage in the start circuit lagging

c) To cause the current in the start circuit leading

Correct Answer : To cause the current in the start circuit leading

37. The synchronous motor stator input is ________

a) DC and AC

b) DC

c) AC

Correct Answer : DC


14/17

38. On a generator is the exiterfield on the ROTOR, what type of machine is

a) Compound machine

b) Externapol machine

c) Internapol machine

Correct Answer : Internapol machine

Explanation : STATORExternalpol

41. Which statement about the resistance in the diagram is correct?

I/A

1 R3

R2

R1

U/V

a.R1> R2

b.R2> R1

c.R3> R1

Correct Answer : R1> R2

Explanation : CURRENT inversely proportional to RESISTANCE

CURRENT RESISTANCE


15/17

42. How much is the voltage Uoin the shown circuit?

20 V 100 Uo

30 V 10

a.10V

b.20V

c.50V

Correct Answer : 10 V

Explanation : Uo= 30 V20 V = 10 V


16/17

43. The direction of the rotation of the Motor in the picture is?

a) Clockwise

b) Counter clockwise

c) There is no movement

Correct Answer : Counter clockwise


17/17

40.The difference between positive and negetive charge is called a potential difference (PD)

measured in volt (V). What is the PD of the charges shown in Figure? PD=?

a.150 V

b.100 V

c.250V

Correct Answer : 250 V

Explanation : Example

-50 OV +200

electrical easa 2

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