CBSE  /  Class 12  /  Physics  /  Current Electricity

  • 1. 
    Which of the following has a negative temperature coefficient of resistance?

  • Tungsten
  • Carbon
  • Nichrome
  • Platinum

  • 2. 
    An electric heating element consumes 500 W, when connected to a 100 V line. If the line voltage becomes 150 V, the power consumed Will be:

  • 500 W
  • 750 W
  • 1000 W
  • 1125 W

  • 3. 
    A uniform w ire connected across a supply produces heat H per second. If wire is cut into three equal parts and all the parts are connected in parallel across the same supply, the heat produced per second will be :

  • \(\frac{H}{9}\)
  • 9 H
  • 3 H
  • \(\frac{H}{3}\)

  • 4. 
    In India electricity is supplied fordomestic use at 220 V. It is supplied at 110 V in U.S.A. If the resistance of a 60 W bulb use in India is R. the resistance of a 60 W bulb for use in USA will be:

  • 2 R
  • R
  • R/2
  • R/4

  • 5. 
    Two bulbs 25 W, 220 V and 100 W, 220 V are given. Which has higher resistance?

  • 25 W
  • 100 W
  • both bulbs have equal resistance
  • resistance of bulbs can not be compared

  • 6. 
    Potentiometer measures the potential difference more accurately than a voltmeter because:

  • It has a wire of high resistance
  • It has a wire of low resistance
  • It does not draw current from external circuit
  • It draws heavy current from external circuit

  • 7. 
    In a Wheatstone bridge, the resistance each arm is 10 Ω. If the resistance galvanometers is also 10 Ω, then effective resistance of the bridge will be :

  • 40 Ω
  • 20 Ω
  • 10 Ω
  • 5 Ω

  • 8. 
    The resistance of an aluminium wire is/i. It is stretched to /i times its original length. Its new resistance will be :

  • nr
  • n²r
  • \(\frac{n^2}{r}\)
  • \(\frac{r}{n^2}\)

  • 9. 
    A wire P is half the diameter and half the length of a wire Q of similar material. The ratio of resistances of P to that 0 is:

  • 4 : 1
  • 8 : 1
  • 2 : 1
  • 1 : 2

  • 10. 
    What is the resistance across A and B in the network in Fig.?

  • R
  • 2 R
  • \(\frac{R}{2}\)
  • 6 R
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