Resistors and Resistance MCQs with Answers

Want create site? Find Free WordPress Themes and plugins.
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


Did you find apk for android? You can find new Free Android Games and apps.