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Resistors and Resistance MCQs with Answers

1. Resistance can be described as the: 
 

A.  opposition to current flow
B.  resist rate of the voltage
C.  current acceptability of a voltage
D.  opposition to voltage flow

 

2. The resistance of a material is most commonly determined by four factors-length, cross-sectional area, type of material and: 
 

A.  voltage
B.  temperature
C.  current
D.  type of supply

 

3. The resistance of a conductor is proportional to its: 
 

A.  cross-sectional area
B.  area
C.  length
D.  current

 

4. The resistance of a conductor is inversely proportional to its: 
 

A.  length
B.  the supply voltage
C.  the type of supply
D.  cross-sectional area

 

5. Look at the following table:    
The above table gives the resistivity of some common materials used in the electrical industry. The best conductor shown on the table is: 
 

A.  silver
B.  gold
C.  nichrome
D.  copper

 

6. Resistivity of a material is defined as the: 
 

A.  amount of opposition to a flow of resistance through 1 meter cube of the material
B.  resistance between the opposite faces of a 1 meter cube at a specified temperature
C.  resistance of 100 meters of 1.5 mm2 copper cable at a specified temperature
D.  resistance between two faces of a 1 mm2 block of that material at 20 °C

 

7. The following formula can be used to determine the resistance of a length of conductor.    
In the formula the symbol ρ stands for the: 
 

A.  cross-sectional area of the conductor in m2
B.  product of the length of the conductor in meters
C.  resistivity of the material on ohm-meters
D.  resistance of the conductor ohms per meter

 

8. A copper cable has a length of 450 m and a cross-sectional area of 4.0 mm2. If the resistivity of the copper is 1.72E-8 Ωm, then the resistance of this cable will be: 
 

A.  193.5 W
B.  0.105 W
C.  1.050 W
D.  1.935 W

 

9. A 10 Ω resistor is to be made from manganin wire with cross-sectional area of 0.2 mm2. If manganin has a resistivity of 48 E–8 Ωm, then the required length of this size manganin wire will be: 
 

A.  4.16 W
B.  41.6 W
C.  6.25 W
D.  62.5 W

 

10. The temperature coefficient of resistance of a material is defined as the change in: 
 

A.  temperature per degree per ohm
B.  resistance per ohm per degree Celsius
C.  cross-sectional area per meter per degree Celsius
D.  length per meter per ohm resistance

 

11. For some materials, an increase in temperature causes an increase in resistance; these materials are said to have a: 
 

A.  standard temperature coefficient
B.  negative temperature coefficient
C.  positive temperature coefficient
D.  ambient temperature coefficient

 

12. Look at the following graph:    
The above graph shows the effect of an increase in temperature on a copper conductor. The graph shows that the increase of resistance plotted against temperature is: 
 

A.  non-linear
B.  not predictable
C.  usually 234.5 °C
D.  basically linear

 

13. The inferred zero formula for determining the resistance of a copper conductor is shown:    
In the formula, the term t2stands for the: 
 

A.  final temperature of the conductor
B.  initial temperature of the conductor
C.  final resistance of the conductor
D.  initial resistance of the conductor

 

14. The resistance of a coil of copper wire is 30 Ω at 15ºC. Its resistance at 75ºC will be: 
 

A.  41.49 W
B.  37.21 W
C.  36.64 W
D.  24.18 W

 

15. An electric motor has a winding resistance of 15 Ω at 20ºC. After running up to temperature at full load the resistance is measured as 19 Ω. The temperature of the windings will now be: 
 

A.  17.56°C
B.  33.57°C
C.  87.86°C
D.  94.20°C

 

16. The temperature coefficient of resistance is defined as the change in: 
 

A.  temperature per degree per ohm resistance
B.  the coefficient of current allowed through a resistance
C.  the resistance of a voltage path per change in current in amperes
D.  resistance per ohm per degree change in temperature

 

17. The above formula can be used to determine the resistance of a conductor using the temperature coefficient of resistance method.    
In the formula the term R1 stands for the: 
 

A.  initial resistance of the conductor
B.  final resistance of the conductor
C.  initial temperature of the conductor
D.  final temperature of the conductor

 

18. If copper conductor has a resistance of 15 Ω at 0ºC, then using the temperature coefficient of resistance method (Note: Consider the temperature coefficient of resistance of copper to be 0.004 27 Ω/Ω/ºC at 0°C.), its resistance at 20ºC will be: 
 

A.  15.82 W
B.  16.28 W
C.  16.60 W
D.  17.65 W

 

19. The supply to a 15A air-conditioning unit consists of copper conductors with a cross-sectional area of 2.5 mm2 and a total resistance of 0.38 Ω. When the air-conditioner is operating, the power lost in the conductors will be: 
 

A.  15 W
B.  57 W
C.  85.5 W
D.  96.5

 

20. Many materials produce an effect known as ‘superconductivity’ when they are cooled below a certain temperature. At the critical temperature: 
 

A.  electrons cannot pass through the material
B.  the material exhibits a super resistance of a very high ohmic value
C.  all the electrons speed up and reach a super-high temperature
D.  electrons can pass through the material with seemingly zero resistance

 

21. When current flows through a conductor, the conductor will heat up. If the conductor temperature exceeds the insulation rating of the cable then the: 
 

A.  insulation can be damaged
B.  circuit current will stop
C.  cable will begin to cool
D.  circuit current increase

 

22. A resistance of 120 Ω is required to carry 200 mA of current. The value of power dissipation required by this resistor is: 
 

A.  12 W
B.  4.8 W
C.  2.4 W
D.  24 W

 

23. Smaller value resistors, from 5 watts to several hundred watts, are commonly: 
 

A.  carbon compound type
B.  carbon film type with conductive paint
C.  wire wound on a ceramic former
D.  metal-oxide on a phenolic base

 

24. The E12 range of preferred values of resistors is based on a tolerance of: 
 

A.  15%
B.  20%
C.  5%
D.  10%

 

25. Look at the following diagram:    
The size of the above resistor is: 
 

A.  4k7 W-5%
B.  4k7 W-10%
C.  470 W-5%
D.  470 W-10%

 

26. Look at the following diagram:    
The above diagram shows the characteristic for a typical PTC thermistor. For an increase in temperature, the resistance of the thermistor will: 
 

A.  decrease
B.  increase
C.  remain the same
D.  become unstable

 

27. Look at the following diagram:    
The above diagram shows the characteristic for a typical NTC thermistor. For an increase in temperature between 50°C and 60°C, the resistance of the thermistor: 
 

A.  increases sharply
B.  decreases at the knee point
C.  decreases in an almost linear manner
D.  will be equal to the resistance at 20°C

 

28. The voltage dependent resistor normally only conducts when the: 
 

A.  circuit current exceeds a certain designed value
B.  power rating of the supply is exceeded
C.  supply voltage needs boosting
D.  supply voltage exceeds a designed limit

 

29. Light-dependent resistors are used to detect light levels such as in PE (photo-electric) cells on power poles to turn street lights on and off, or to control other night lighting. When light falls on the resistor: 
 

A.  its resistance changes
B.  a voltage is produced
C.  it generates a current
D.  its resistance always remain the same

 

30. Liquid resistors are often used in motor starters. One advantage of liquid resistance is that the resistance value: 
 

A.  increases as the temperature rises
B.  decreases as the temperature rises
C.  decreases as the temperature decreases
D.  increases as the temperature increases