20625155
Descripción
Test por Owen Ryan Ang, actualizado hace más de 1 año
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Creado por Owen Ryan Ang
hace casi 5 años
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Pregunta 1
Pregunta
What are the minimum requirements to cause the flow of current?
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A voltage source, an ammeter, a conductor and an insulator
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A voltage source, a switch and a resistor
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A voltage source and a conductor
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A voltage source, a conductor and an insulator
Pregunta 2
Pregunta
Out of the following, select the best conductor of electricity.
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Graphite
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China Clay
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Porcelain
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None of these
Pregunta 3
Pregunta
Which of the following statements is correct?
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The resistance does not play an important role in electrical engineering.
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The resistance of a wire does not depend upon its material.
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The resistance of most of the materials is independent of the temperature.
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The resistance of conductor is the hindrance by which the conductor opposes the flow of the current.
Pregunta 4
Pregunta
Resistance of a conductor increases when
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its length increases
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its area increases
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both length and area increases
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specific resistance is kept constant
Pregunta 5
Pregunta
The specific resistance ρ depends upon
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The area of cross-section and the length of the conductor
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The material of the conductor, its area of cress-section and length
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The nature of the material of the conductor only
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The area of cross-section of the conductor
Pregunta 6
Pregunta
The specific resistance ρ is defined as
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resistance of a conductor which has a length of 1 m and cross-section of 1 m2 at 20C
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resistance of any conductor at 25C
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resistance of any conductor at 20C
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resistance of a conductor which has a length of 1 m and cross-section of 1 cm2 at 20C
Pregunta 7
Pregunta
The resistance of a conductor, when its temperature is increased
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remains constant
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increases
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varies
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decreases
Pregunta 8
Pregunta
It was experimentally found by James Prescott Joule that the heat produced in a current carrying conductor is proportional to
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the square of the current
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square of resistance
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the current
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inversely proportional to time
Pregunta 9
Pregunta
The value of Joule's mechanical equivalent of heat, J, is equal to
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4.2 calories per Joule
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2.4 Joules per calorie
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4.2 Joules per calorie
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4.2 Joules
Pregunta 10
Pregunta
Temperature coefficient of a conductor is defined as the
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increase in resistance per ohm per degree centigrade
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increase in resistance per degree centigrade
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increase in resistance per degree absolute
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decrease in resistance per ohm per degree centigrade
Pregunta 11
Pregunta
When current flows in a conductor, heat is produced because
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heat α I²
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of electronic collision
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of interatomic collision
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of Joule's law
Pregunta 12
Pregunta
Heating effect of current has undesirable side effect in
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electric oven
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electric iron
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immersion heater
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vacuum cleaner
Pregunta 13
Pregunta
The resistance of carbon (filament in carbon-filament lamps) when its temperature is decreased
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increases
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decreases
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remains the same
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increases enormously
Pregunta 14
Pregunta
The curve representing Ohm's law is
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a parabola
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linear
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sine function
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a hyperbola
Pregunta 15
Pregunta
The condition in Ohm's law is that
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ratio V/I should be constant
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current should be proportional to voltage
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the temperature should remain constant
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the temperature should vary
Pregunta 16
Pregunta
Ohm's law does not apply to
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conductors
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conductors when there is change in temperature
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semiconductor
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a.c. circuit
Pregunta 17
Pregunta
Ohm's law is applicable to
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electric arc
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rectifying devices
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gas discharge lamps
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none of these
Pregunta 18
Pregunta
Ohm's law can be applied with certain reservations to
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rectifying devices
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semiconductors
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electrolytes
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thermionic valves
Pregunta 19
Pregunta
The presence of an electric current is made known by
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flashing
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effects produced
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cracking
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electric shock
Pregunta 20
Pregunta
An electric current can neither be ____ nor ____.
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felt, seen
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seen, touched
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seen, produced by any effect
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produced, felt
Pregunta 21
Pregunta
The presence of the current is only made known by the effect it produces. Three important effects are
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heating, electric shock and generation
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generation, chemical and electric shock
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heating, magnetic and electric shock
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heating, magnetic and chemical
Pregunta 22
Pregunta
Voltage applied across a circuit, acts as
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mass of electrons
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negative ions
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a component of current
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a force
Pregunta 23
Pregunta
In a series circuit the current is
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constant
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always zero
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proportional to the resistance
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different from resistors
Pregunta 24
Pregunta
In a parallel circuit the potential difference across the resistance
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varies
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is different from the applied voltage
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is sometimes constant
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is always constant
Pregunta 25
Pregunta
The resistance R1 and R2 are connected in parallel. The ratio of values of resistance R1 : R2 is 4 : 1. The currents in R1 : R2 will be equal to
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1 : 4
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1 : 1
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4 : 1
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4 : 4
Pregunta 26
Pregunta
A resistance of 4 ohms is connected across 100 V supply. When another resistor 'R' ohms is connected in parallel with 4 ohms, the total current taken from supply was found to be 50 A. The value of resistance 'R' is
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2 ohms
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3 ohms
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5 ohms
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4 ohms
Pregunta 27
Pregunta
The voltage applied across an electric press was reduced by 50%. The power consumed by the press will be reduced by
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25%
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75%
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60%
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50%
Pregunta 28
Pregunta
Two electric presses are connected in parallel. The resistance of the first press is 100 ohms and that of the second is 300 ohms. The total current taken by both the presses is 4 A. The ratio of current taken by first : second will be equal to
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2 : 3
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1 : 3
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3 : 1
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1.2 : 3
Pregunta 29
Pregunta
Three elements having conductance G1. G2 and G3 are connected in parallel. Their combined conductance will be
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G1 + G2 + G3
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1/(G1 + G2 + G3)
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(G1G2 + G2G3 + G3G1)/(G1 + G2 + G3)
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1/(1/G1 + 1/G2 + 1/G3)
Pregunta 30
Pregunta
Four resistance R1, R2, R3 and R4 are connected in series against 220 V supply. The resistances are such that R1 > R2 > R3 > R4. The least power consumption will be in
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resistor R1
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resistor R4
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resistor R3
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resistor R2
Pregunta 31
Pregunta
When current flows through heater coil it glows but supply wiring does not glow because
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supply wiring is covered with insulation layer
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current through supply line flows at slower speed
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supply wires are made of superior material
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resistance of heater coil is more than that of supply wires
Pregunta 32
Pregunta
Resistors commonly used in power circuits are
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carbon resistors
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etched circuit resistors
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wire wound resistors
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deposited metal resistors
Pregunta 33
Pregunta
International ohm is defined in terms of resistance of
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a column of mercury
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a cube of carbon
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unit length of metal wire
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a cube of copper
Pregunta 34
Pregunta
Which of the following has negative coefficient of resistance?
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wire wound resistor
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non-metals
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thermistor
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metals
Pregunta 35
Pregunta
The current carrying capability of the fuse material depends on
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length
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material
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cross-sectional area
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all of these
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