When three identical bulbs of 60 W, 200 V rating are connected in series to a 200 V supply, the power drawn by them will be:
  • 20 W
  • 60 W
  • 180 W
  • 10 W
n resistances, each of R Ω, are connected in parallel gives an equivalent resistance of R Ω. If these resistances were , connected in series, the combination would have a resistance in Ω is equal to
  • n²R
  • R/n²
  • R/n
  • nR
Why is the Wheatstone bridge more accurate than other methods of measuring resistances:
  • It is a null method
  • It is based on Kirchhoffs laws
  • It has four resistances
  • It does not involve ohm's law
A potential difference of 10 V is applied across a conductance of 2 S. The current in the conductor will be :
  • 20 A
  • 5 A
  • 0.2 A
  • None of these
Ohm's law is valid when the temperature of conductor is :
  • very low
  • very high
  • varying
  • constant
The emf of a car battery is about:
  • 2.5 V
  • 4.5 V
  • 8.6 V
  • 12 V
Emf is measured in :
  • joule
  • joule/coulomb
  • joule-coulombs
  • joule/coulomb/metre
1 kilowatt hour is commonly known as :
  • unit
  • 1 faraday
  • 1 curie
  • None of these
How many joules are equal to I kWh?
  • 3.6 × 104
  • 3.6 × 105
  • 3.6 × 106
  • None of these
The temperature coefficient of resistance is expressed in :
  • °C
  • °C-1
  • m°C-1
  • None of these
Copper wire is used as connecting wire because :
  • copper has high electrical resistivity
  • copper has low electrical resistivity
  • copper has low electrical conductivity
  • copper has high value of elasticity
The heat sensitive device whose resistivity changes very rapidly with change of temperature is called a :
  • resistor
  • super-conductor
  • thermocouple
  • thermistor
The phenomenon of super-conductivity was discovered by :
  • Ohm
  • Onnes
  • Edison
  • None of these
The specific resistance of a conductor increases with :
  • increase in temperature
  • increase in cross-sectional area
  • decrease in length
  • decrease in cross-sectional area
In an experiment with potentiometer, null point with a cell is found at 240 cm. When the cell is shunted with a resistance 2 Ω, the null point becomes 120 cm internal resistance of cell is :
  • 4 Ω
  • 2 Ω
  • 1 Ω
  • \(\frac{1}{2}\) Ω
Two conductors of equal length and radii the ratio of 2 : 3 are; connected in parallel the source of electricity. The ratio of the velocity of electrons in the conductor be :
  • 2 : 3
  • 4 : 9
  • 1 : 1
  • 3 : 2
In questions 38, the maximum value of current (lmax) is given by the condition :
  • lmax = α - \(\frac{β^2}{2γ}\)
  • lmax = α - \(\frac{β^2}{2α}\)
  • lmax = α - \(\frac{γ^2}{2β}\)
  • None of these
In questions 38, the line (t) after which the value of current reaches a maximum values given by :
  • t = \(\frac{α}{β}\)
  • t = \(\frac{β}{α}\)
  • t = \(\frac{β}{γ}\ )
  • t = \(\frac{γ}{β}\)
The smallest resistance that can be obtained by the combination of n resistors each resistance r is :
  • \(\frac{r}{n}\)
  • nr
  • \(\frac{n}{r}\)
  • n²r
Which of the following has a negative temperature coefficient of resistance?
  • Tungsten
  • Carbon
  • Nichrome
  • Platinum
0 h : 0 m : 1 s

Answered Not Answered Not Visited Correct : 0 Incorrect : 0