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