MCQs On Basic Electrical Engineering Concepts

MARCH, 2018

1) The diameter of an atom is about:

- 10
^{-10}m - 10
^{-02}m - 10
^{-08}^{ }m - 10
^{-15}^{ }m

2) 1 cm^{3} of copper at room temperature has about:

- 2×10
^{2}free electrons - 20×10
^{3}free electrons - 8.5×10
^{22}free electrons - 3×10
^{21}free electrons

3) The charge of a proton is _______ the charge of electron.

- Equal to
- Less than
- About 625 times
- 200 times

4) If the number of valence electrons of an atom is 4, then the substance is usually a

- Conductor
- Insulator
- Semiconductor
- None of the above

5) The electrons in the last orbit of an atom are called

- Free electrons
- Bound electrons
- Valence electrons
- Thermionic electrons

- 625×10
^{16}electrons - 6.25×10
^{16}electrons - 62.5×10
^{16}electrons - 0.625×10
^{16}electrons

7) The electric current is due to the flow of

- Positive charges only
- Negative charges only
- Both positive and negative charges
- Neutral particles only

8) E.M.F in a circuit

- Increases circuit resistance
- Decreases circuit resistance
- Maintains potential difference
- None of the above

9) Potential difference has the unit of

- Charge
- Energy
- Power
- None of the above

10) The electric current in a liquid is due to the flow of

- Electrons only
- Protons only
- Negative and positive ions
- Electrons and positive ions

11) The electric current in a discharge tube containing a gas is due to

- Electrons only
- Positive ions only
- Positive and negative ions
- Electrons and positive ions

12) Electric current is a

- Scalar quantity
- Vector quantity
- Number only
- None of the above

^{3}seconds. The current is

- 1.6×10
^{-7}A - 2×10
^{-7}A - 1×10
^{-7}A - 2.6×10
^{-7}A

- 3.33×10
^{-3}seconds - 6×10
^{-3}seconds - 2 seconds
- None of the above

15) The specific resistance of a wire depends upon its

- Length
- Cross sectional area
- Dimension
- Material

- 1×10
^{3}seconds C - 2.4×10
^{3}seconds C - 3.6×10
^{4}seconds C - 1.6×10
^{2}seconds C

17) A length of a wire has a resistance of 6 Ω. The resistance of the wire of the same material three times as long and twice the cross sectional area will be

- 36 Ω
- 9 Ω
- 1 Ω
- 12 Ω

- 1 ms
^{-1} - 10
^{-5}ms^{-1} - 10
^{6}ms^{-1} - 3×10
^{8}ms^{-1}

19) Conductivity is the reciprocal of

- Current density
- Reactance
- Resistivity
- Inductance

20) The potential difference of an energy source that provides 5 mJ of energy for every micro coulomb of charge that flows is

- 5 V
- 50 V
- 500 V
- 50 kV

21) The specific resistance of a metallic conductor ________ with the rise in temperature

- Increases
- Decreases
- Remains same
- Decreases first than start increases

22) Insulators have ________ temperature coefficient of resistance

- Zero
- Negative
- Positive
- None of the above

23) Eureka has __________ temperature coefficient of resistance

- Positive
- Negative
- Almost zero
- None of the above

24) What quantity of charge must be delivered by a battery with a potential difference of 100 V to do 500 J of work

- 5 C
- 0.5 C
- 50 C
- 500 C

25) A piece of aluminium wire is stretched to reduce its diameter to half of its original value. Its resistance will become

- Two times
- Half
- Sixteen times
- Eight times

26) Semiconductor have ______ temperature coefficient of resistance

- Positive
- Negative
- Zero
- None of the above

- 1 ms
^{-1} - 10 ms
^{-3} - 10
^{6}ms^{-1} - 3×10
^{8}ms^{-1}

^{2}in area of cross-section is 1.6×10

^{-8}Ω. Its specific resistance will be

- 1.6×10
^{-8}Ωm - 3.2×10
^{-8}Ωm - 6.4×10
^{-8}Ωm - 0.16×10
^{-8}Ωm

29) The value of α ( temperature coefficient of resistance ) depends on

- Length of the material
- Cross-sectional area of the material
- Volume of the material
- Nature of the material and temperature

^{o}is stretched till its length is increased ‘n’ times of its original length. Its resistance will now be

- n
^{2}R^{o} - R
^{o}/ n^{2} - nR
^{o} - n
^{3}R^{o}

31) The resistivity of a material 2 × 10^{-8} Ωm. What will be the resistance of a hollow pipe of the material of length 1 m and having inner and outer radii of 10 cm and 20 cm respectively.

- 2.0 × 10
^{-4}Ω - 2.1 × 10
^{-7}Ω - 2.0 × 10
^{-5}Ω - 2.0 × 10
^{-3}Ω

32) The example of non ohmic resistance is

- Copper wire
- Carbon resistance
- Aluminium wire
- Tungsten wire
- All of the above

33) A copper wire is stretched so that its length is increased by 0.1 %. The change in its resistance is

- 0.1 %
- 0.2 %
- 0.3 %
- 0.4 %

34) If an electric current is passed through a nerve, the man

- Begins to laugh
- Gets shocked
- Is excited
- Becomes insensitive to pain

35) The temperature coefficient of resistance of a wire is~~ ~~0.00125~~ ~~per °C. at 300 K, its resistance is~~ ~~~~ ~~1 Ω. The resistance of the wire will be 2~~ ~~Ω at

- 1154 K
- 1100 K
- 1400 K
- 1127 K

36) Ampere-Hour is the unit of

- Quantity of electricity
- Energy
- Power
- Conductivity

37) The resistance of a conductor is 5 Ω at 50 °C and 6 Ω at 100 °C. What is the resistance at 0 °C.

- 1 Ω
- 2 Ω
- 3 Ω
- 4 Ω

^{0}of a conductor is 1/236 per °C. The value of α

^{18}will be

- 1/218 per °C
- 1/244 per °C
- 1/254 per °C
- 1/264 per °C

^{0}of a conductor is 1/255 per °C. The value of α

^{20}will be

- 1/300 per °C
- 1/230 per °C
- 1/250 per °C
- 1/265 per °C

^{50}of a conductor is 1/230 per °C. The value of α

^{0}will be

- 1/180 per °C
- 1/280 per °C
- 1/380 per °C
- 1/250 per °C

41) The number of free electrons passing through the filament of an electric bulb in one hour when the current through the current through it is 0.32 A filament will

- 3 × 10
^{22} - 2× 10
^{26} - 7.2 × 10
^{19} - 3 × 10
^{21}

42) In which of the following substances the resistance decreases with increase in temperature

- Carbon
- Constantan
- Copper
- Silver

43) A wire having very high value of conductance is said to be

- Very good conductor
- Moderately good conductor
- Insulator
- None of the above

44) An electric heater is marked 2000 W, 200 V. The resistance of the coil is

- 0.1 Ω
- 20 Ω
- 1/20 Ω
- 200 Ω

45) The current in a circuit having constant resistance is tripled. The power increases

- 1/9 times
- 3 times
- 9 times
- 1/3 times

46) What voltage drop will be there across a 1 KW electric heater whose resistance when hot is 40 Ω.

- 100 V
- 50 V
- 150 V
- 200 V

_{1}dissipates the power P when connected to a certain generator. If resistance R

_{2}is put in series with R

_{1}, the power dissipated by R

_{1}

- Decreases
- Increases
- Remains the same
- Any of the above depending upon the values of R
_{1}and R_{2}

48) In case of liquids, Ohm’s law is

- Fully obeyed
- Partially obeyed
- There is no relation there between current and P.D
- None of the above

_{1}and R

_{2}then

- R
_{1}= 2 R_{2} - R
_{2}= 2 R_{1} - R
_{2}= 4 R_{1} - R
_{1}= 4 R_{2}

50) A copper wire a resistance of 10 Ω. It is stretched by one-tenth of its original length. Then its resistance will be

- 10 Ω
- 12.1 Ω
- 9 Ω
- 11 Ω

^{20}electrons each having a charge of 1.6×10

^{-19}C pass from a point X to a point Y in 0.1 seconds. The current flowing is

- 16 A
- 1.6 A
- 160 A
- 1 A

52) No current flows between two charged bodies if they had same

- Capacity
- Potential
- Charge
- None of the above

53) A carbon electrode has a resistance of 0.125 Ω at 20 °C. The temperature coefficient of carbon is -0.0005 at 20 °C. What will be the resistance of electrode at 85 °C

- 4 Ω
- 0.5 Ω
- 1.2 Ω
- 0.121 Ω

- 48 × 10
^{-8}Ωm - 40 × 10
^{8}Ωm - 4 × 10
^{-6}Ωm - 4.8 × 10
^{-8}Ωm

55) Ampere-second is the unit of

- Power
- Energy
- E.M.F
- Charge

56) The percentage by which the incandescence of lamp decreases due to drop of current by 3% is

- 6%
- 3%
- 9%
- 12%

_{A}and R

_{B}respectively with R

_{A}<R

_{B}. The resistivity of their materials are ρA and ρB. Then

- ρA < ρB
- ρA = ρB
- ρA < ρB
- Insufficient information

58) As the temperature of a metallic resistor is increased, the product of its resistivity and conductivity

- Increased
- Decreased
- Remains constant
- May increased or decreased

59) A resistor develops 400 J of thermal energy in seconds when a current of 2 A is passed through it. The resistance of the resistor is

- 10 Ω
- 20 Ω
- 5 Ω
- 40 Ω

^{6}m/s. The electric current of a point on the circle is

- 1×10
^{-12}A - 4×10
^{-7}A - 2×10
^{-6}A - None of the above

61) The resistance of a human body is about

- 200 Ω
- 1000 Ω
- 25 Ω
- 10 Ω

62) The hot resistance of an electric bulb filament is higher than its cold resistance because the temperature coefficient of filament is

- Zero
- Positive
- Negative
- None of the above

63) A nichrome wire used as a heater coil has a resistance of 2 Ω/m. For a heater of 1 kW at 200 V, the length of the wire required is

- 80 m
- 40 m
- 20 m
- 24 m

64) When 1 V is applied in a circuit, a current of 1 μ A flows through it. The conductance of the circuit is

- 1 μ mho
- 10 μ mho
- 100 μ mho
- None of the above

- 20 μS
- 14.81 μS
- 18.71 μS
- 24.5 μS

66) How much voltage is necessary to create a flow of 0.24 C in 0.8 seconds through a resistance of 500 Ω.

- 50 V
- 300 V
- 150 V
- 75 V

- 5.4 kWh
- 2.89 kWh
- 1.89 kWh
- 10.89 kWh

- V
^{2}G - V
^{2}/ G - G
^{2}V - G
^{2}/ V

69) On the voltage versus current graph of a 10 kΩ resistor, what is the total change in voltage when the current changes from 1 mA to 5.5 mA

- 55 V
- 110 V
- 45 V
- 50 V

i = 5 cos πt A

The~~ ~~power delivered to the element at t = 3 ms when the voltage across the element is 3t is given by

- 18.43 W
- 26.4 W
- 53.48 W
- 63.28 W

^{2}is carrying a current of 10 A. If the number density of conduction electrons is 10

^{-28}m

^{-3}. The drift velocity of conduction electrons is

- 1 / 160 ms
^{-1} - 1 / 20 ms
^{-1} - 1 / 30 ms
^{-1} - 1 / 80 ms
^{-1}

- 2 × 10
^{-6}Ω - 0.8 × 10
^{-6}Ω - 1.6 × 10 Ω
- 4 × 10
^{-6}Ω

- 1/3 α
_{o}°C - 1/α
_{o}°C - 1/2 α
_{o}°C - 1/6 α
_{o}°C

74) If a wire is melted and recast to half of its length, then the new resistance is

- R/4
- R/2
- R
- 2R

_{A}= 600 Ω and R

_{B}= 100 Ω. The number of times A is longer than B is

- 6
- 2
- 4
- 5

76) The resistivity of a wire depends on

- Length
- Material
- Cross-sectional area
- None of the above

77) Kirchhoff’s second law is based on law of conservation of

- Charge
- Energy
- Momentum
- Mass

78) The mass of the proton is roughly how many times the mass of an electron?

- 184000
- 18400
- 1840
- 184

- Joule / Second
- Ampere / Volt
- Ampere x Volts
- (Ampere)
^{2}x Ohm

- 36 x 10
^{5}watt - 36 x 10
^{5}ergs - 36 x 10
^{5}joules - 36 x 10
^{5}B.T.U

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