Important Basic Electrical MCQs
In this post, some of the important Basic Electrical mcqs are given. It includes heating material, Eureka, diameter of resistance material, negative temperature co-efficient, specific gravity of copper, colour code of resistance, ideal voltage source, ideal resistance of practical voltage source, ideal current source, lowest current noise level, highest power rating resistance, non-linear characteristics of resistor and voltage across short circuit terminals.
Basic Electrical MCQs 61 to 65
61 As the temperature increases, the resistivity of metal
( a )Increases
( b )Decreases
( c )Does not affect
( d )Any of the above
Correct Answer ( a ): Increases
62 The best material for heating element is
( a )Copper
( b )Aluminium
( c )Manganin
( d )Nichrome
Correct Answer ( d ): Nichrome
63 The Eureka is alloy of
( a )Copper, aluminium
( b )Copper, nickel
( c )Aluminium, nickel
( d )Copper, silver
Correct Answer ( b ): Copper, nickel
64 If the diameter of wire is reduced one half, the resistance of the wire becomes
( a )Double
( b )One – half
( c )Four times
( d )One fourth
Correct Answer ( c ): Four times
A = (π/4) d2
Diameter reduces to one half
A = (π/4) (d/2)2
A = (π/4) (d)2 / 4
R = ρL/A
If the diameter becomes one half, area is reduced to ¼ times. This will result in resistance reduces to ¼ times.
65 Which of the following material is mechanically strong?
( a )Hard copper
( b )Pure aluminium
( c )Pure copper
( d )Nickel
Correct Answer ( a ): Hard copper
As the hard copper is pulled through dies, its crystalline structure is break down therefore the hard drawn copper is mechanically stronger than annealed copper.
Basic Electrical MCQs 66 to 70
66 Which of the following has negative temperature coefficient of resistance?
( a )Silicon
( b )Copper
( c )Aluminium
( d )Silver
Correct Answer ( a ): Silicon
The semiconductor material has negative temperature co-efficient because as the temperature increases, the resistance of semiconductor material decreases.
67 The specific gravity of copper is approximately _____ times that of aluminium.
( a ) 1 / 4
( b ) 1 / 2
( c )2
( d )3
Correct Answer ( d ): 3
The specific gravity of copper is 8.9 whereas aluminium is 2.7 therefore specific gravity of copper is 3 times that of aluminium.
68 The resistance of the black, brown, green colour resistor is
( a )1 x 105 ± 20%
( b )10 x 106 ± 20%
( c )1 x 104 ± 20%
( d )2 x 106 ± 20%
Correct Answer ( a ): 1 x 105 ± 20%
Colour code digits
Black = 0
Brown = 1
Green colour = 5 ( 105 )
No colour = ± 20
Total resistance = 1 x 105 ± 20%
69 The resistance of red, orange, white and gold colour resistor is
( a )32 x 108 ± 10%
( b )42 x 108 ± 5%
( c )23 x 109 ± 5%
( d )24 x 108 ± 10%
Correct Answer ( c ): 23 x 109 ± 5%
Colour code digits
Red = 2
Orange = 3
White = 9 ( 109 )
Gold = ± 5%
Resistance = 23 x 109 ± 5%
70 The tolerance of the resistor has three colours of black, brown and red is
( a ) ± 5%
( b ) ± 10%
( c ) ± 20%
( d )0.2
Correct Answer ( c ): ± 20%
Tolerance for colour code
Gold = ± 5%
Silver = ± 10%
No colour = ± 20%
Basic Electrical MCQs 71 to 75
71 The ideal voltage source has internal resistance of
( a )Infinite
( b )100 kΩ
( c )20 Ω
( d )Zero ohm
Correct Answer ( d ): Zero ohm
72 The internal resistance of practical voltage source is
( a )Infinite
( b )Very small
( c )Zero
( d )None of the above
Correct Answer ( b ): Very small
The ideal voltage source has zero internal resistance so total input voltage is available for load but practical it is not possible so every voltage source has small internal resistance is in series.
73 The internal resistance of the ideal current source is
( a )Zero ohm
( b )2.0 ohm
( c )100 ohm
( d )Infinite
Correct Answer ( d ): Infinite
Ideal current source has infinite resistance is in parallel therefore most of current available for load whereas practical current source has high resistance is in parallel.
74 Which of the following should be power rating of carbon composition resistors?
( a )1 kilowatt
( b )100 watt
( c )10 watt
( d )2 watt
Correct Answer ( d ): 2 watt
The power rating of carbon composition is available up to 5 watt.
75 Which of the following resistor has lowest current noise level?
( a )Carbon composition
( b )Deposited carbon
( c )Wire wound
( d )None of the above
Correct Answer ( c ): Wire wound
The wire wound resistor has lowest noise level.
For detail about Noise level in resistors
Basic Electrical MCQs 76 to 80
76 Which of the following resistor has highest power rating?
( a )Carbon composition
( b )Wire wound
( c )Metal film
( d )Deposited carbon
Correct Answer ( b ): Wire wound
77 Which of the following resistor has non – linear characteristics?
( a )Diodes
( b )Thermistors
( c )Incandescent lamp
( d )All of the above
Correct Answer ( d ): All of the above
The V-I characteristics of diode, thermistor and incandescent lamp is non – linear.
78 Three resistances of 3Ω are connected in parallel the equivalent resistance is _____
( a )9 Ω
( b )(1 / 3) Ω
( c )3 Ω
( d )1 Ω
Correct Answer ( d ): 1 Ω
If three equal resistances of 3 ohm are connected in parallel, its equivalent resistance becomes 1/3 of 3 ohm resistor. Similarly, if 5 equal resistances of 10 ohm are connected in parallel, its equivalent resistance becomes 1/5 of 10 ohm resistor.
79 Which of the following relation is true for parallel circuit?
( a )G = G1 + G2 + …….
( b )R = R1 + R2 + …….
( c )I1 = I2 = ……
( d )V = V1 + V2 + …….
Correct Answer ( a ): G = G1 + G2 + …….
G = Conductor
In parallel circuit 1/R = 1/R1 + 1/R2 +…..
So G = G1 + G2 +…….
80 The voltage across short circuit terminal in any terminal is equal to
( a )Supply voltage
( b )Maximum voltage
( c )RMS voltage
( d )Zero voltage
Correct Answer ( d ): Zero voltage
Basic Electrical MCQs PDF
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