JEE Main & Advanced Physics Alternating Current / प्रत्यावर्ती धारा Question Bank

done Alternating Current, Voltage and Power Total Questions - 46

• question_answer1)
  The power is transmitted from a power house on high voltage ac because                                           [CPMT 1984, 85]
  A)
             Electric current travels faster at higher volts done clear
  B)
             It is more economical due to less power wastage done clear
  C)
             It is difficult to generate power at low voltage done clear
  D)
             Chances of stealing transmission lines are minimized done clear
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• question_answer2)
  The potential difference V and the current i flowing through an instrument in an ac circuit of frequency f are given by \[V=5\cos \omega \,t\] volts and I = 2 sin wt amperes (where w = 2pf). The power dissipated in the instrument is [CPMT 1977, 80; MP PET 1999]
  A)
             Zero                                          done clear
  B)
             10 W done clear
  C)
             5 W                                           done clear
  D)
              2.5 W done clear
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• question_answer3)
  In an ac circuit, V and I are given by V = 100 sin (100 t) volts, \[I=100\sin \,\left( 100t+\frac{\pi }{3} \right)\,mA\]. The power dissipated in circuit is [MP PET 1989; RPET 1999; MP PMT 1999, 2002]
  A)
             104 watt                                  done clear
  B)
             10 watt done clear
  C)
             2.5 watt                                  done clear
  D)
             5 watt done clear
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• question_answer4)
  Alternating current can not be measured by dc ammeter because                                            [AIEEE 2004]
  A)
             ac cannot pass through dc ammeter done clear
  B)
             Average value of complete cycle is zero done clear
  C)
             ac is virtual done clear
  D)
             ac changes its direction done clear
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• question_answer5)
  The resistance of a coil for dc is in ohms. In ac, the resistance                                      [CPMT 1987]
  A)
             Will remain same                done clear
  B)
             Will increase done clear
  C)
             Will decrease                        done clear
  D)
              Will be zero done clear
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• question_answer6)
  If instantaneous current is given by \[i=4\cos \,(\omega \,t+\varphi )\] amperes, then the r.m.s. value of current is                    [RPET 2000]
  A)
             4 amperes                              done clear
  B)
             \[2\sqrt{2}\] amperes done clear
  C)
             \[4\sqrt{2}\] amperes       done clear
  D)
             Zero amperes done clear
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• question_answer7)
  In an ac circuit, peak value of voltage is 423 volts. Its effective voltage is                                                 [JIPMER 1997]
  A)
             400 volts                                 done clear
  B)
              323 volts done clear
  C)
             300 volts                                 done clear
  D)
              340 volts done clear
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• question_answer8)
  In an ac circuit I = 100 sin 200 pt. The time required for the current to achieve its peak value will be  [DPMT 2003]
  A)
             \[\frac{1}{100}sec\]           done clear
  B)
             \[\frac{1}{200}sec\] done clear
  C)
             \[\frac{1}{300}sec\]           done clear
  D)
             \[\frac{1}{400}sec\] done clear
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• question_answer9)
  The peak value of an Alternating current is 6 amp, then r.m.s. value of current will be
  A)
             3 A done clear
  B)
             \[3\sqrt{3}\]A done clear
  C)
             \[3\sqrt{2}\]A                       done clear
  D)
             \[2\sqrt{3}\]A done clear
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• question_answer10)
  A generator produces a voltage that is given by \[V=240\sin 120\,t\], where t is in seconds. The frequency and r.m.s. voltage are                                            [MP PET 1993; MP PMT 1990]
  A)
             60 Hz and 240 V                    done clear
  B)
             19 Hz and 120 V done clear
  C)
             19 Hz and 170 V                    done clear
  D)
             754 Hz and 70 V done clear
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• question_answer11)
  If \[{{E}_{0}}\] represents the peak value of the voltage in an ac circuit, the r.m.s. value of the voltage will be [CPMT 1972; MP PMT 1996]
  A)
             \[\frac{{{E}_{0}}}{\pi }\]   done clear
  B)
             \[\frac{{{E}_{0}}}{2}\] done clear
  C)
             \[\frac{{{E}_{0}}}{\sqrt{\pi }}\]                                          done clear
  D)
             \[\frac{{{E}_{0}}}{\sqrt{2}}\] done clear
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• question_answer12)
  The peak value of 220 volts of ac mains is [CPMT 1990; MP PMT 1999; MP PET 2000; RPET2001]
  A)
             155.6 volts                              done clear
  B)
              220.0 volts done clear
  C)
             311.0 volts                              done clear
  D)
              440 volts done clear
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• question_answer13)
  A sinusoidal ac current flows through a resistor of resistance R. If the peak current is\[{{I}_{p}}\], then the power dissipated is   [MP PMT 1991]
  A)
             \[I_{p}^{2}R\cos \theta \]       done clear
  B)
             \[\frac{1}{2}I_{p}^{2}R\] done clear
  C)
             \[\frac{4}{\pi }I_{p}^{2}R\]     done clear
  D)
             \[\frac{1}{\pi }I_{p}^{2}R\] done clear
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• question_answer14)
  A 40 W electric heater is connected to a 200 V, 50 Hz mains supply. The peak value of electric current flowing in the circuit is approximately                                            [MP PET 1992]
  A)
             2.5 A                                         done clear
  B)
             5.0 A done clear
  C)
             7 A done clear
  D)
             10 A done clear
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• question_answer15)
  The frequency of ac mains in India is [NCERT 1974; MP PMT/PET 1988; RPMT 1997; RPET 2000]
  A)
             30 c/s or Hz                            done clear
  B)
             50 c/s or Hz done clear
  C)
             60 c/s or Hz                            done clear
  D)
             120 c/s or Hz done clear
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• question_answer16)
  The r.m.s. value of an ac of 50 Hz is 10 amp. The time taken by the alternating current in reaching from zero to maximum value and the peak value of current will be [MP PET 1993; KCET 2003]
  A)
             2 ´ 10?2 sec and 14.14 amp done clear
  B)
             1 ´ 10?2 sec and 7.07 amp done clear
  C)
             5 ´ 10?3 sec and 7.07 amp done clear
  D)
             5 ´ 10?3 sec and 14.14 amp done clear
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• question_answer17)
  The root mean square value of the alternating current is equal to                                             [MP PMT 1993]
  A)
             Twice the peak value done clear
  B)
             Half the peak value done clear
  C)
             \[\frac{1}{\sqrt{2}}\] times the peak value done clear
  D)
             Equal to the peak value done clear
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• question_answer18)
  The peak value of an alternating e.m.f. E is given by \[E={{E}_{0}}\cos \omega \,t\]is 10 volts and its frequency is 50 Hz. At time\[t=\frac{1}{600}sec\], the instantaneous e.m.f. is [MP PMT 1990; MP PET 2004]
  A)
             10 V                                          done clear
  B)
             \[5\sqrt{3}\,V\] done clear
  C)
             5 V done clear
  D)
              1 V done clear
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• question_answer19)
  If a current I given by \[{{I}_{0}}\sin \,\left( \omega \,t-\frac{\pi }{2} \right)\] flows in an ac circuit across which an ac potential of \[E={{E}_{0}}\sin \omega \,t\] has been applied, then the power consumption P in the circuit will be [CPMT 1986; Roorkee 1992; SCRA 1996; MP PMT 1994; RPET 2001; MP PET 2001, 02]
  A)
             \[P=\frac{{{E}_{0}}{{I}_{0}}}{\sqrt{2}}\]                        done clear
  B)
             \[P=\sqrt{2}{{E}_{0}}{{I}_{0}}\] done clear
  C)
             \[P=\frac{{{E}_{0}}{{I}_{0}}}{2}\]                                      done clear
  D)
             P = 0 done clear
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• question_answer20)
  In an ac circuit, the instantaneous values of e.m.f. and current are e = 200 sin 314 t volt and\[i=\sin \,\left( 314t+\frac{\pi }{3} \right)\] ampere. The average power consumed in watt is  [NCERT 1990; RPMT 1997]
  A)
             200 done clear
  B)
             100 done clear
  C)
             50   done clear
  D)
              25 done clear
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• question_answer21)
  An ac generator produced an output voltage \[E=170\sin 377\,t\,volts\], where t is in seconds. The frequency of ac voltage is                                                                        [MP PET 1994]
  A)
             50 Hz                                        done clear
  B)
             110 Hz done clear
  C)
             60 Hz                                        done clear
  D)
             230 Hz done clear
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• question_answer22)
  In general in an alternating current circuit      [MP PMT 1994]
  A)
             The average value of current is zero done clear
  B)
             The average value of square of the current is zero done clear
  C)
             Average power dissipation is zero done clear
  D)
             The phase difference between voltage and current is zero done clear
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• question_answer23)
  An alternating current is given by the equation \[i={{i}_{1}}\cos \omega \,t+{{i}_{2}}\sin \omega \,t\]. The r.m.s. current is given by [MP PMT 1994]
  A)
             \[\frac{1}{\sqrt{2}}({{i}_{1}}+{{i}_{2}})\]                       done clear
  B)
             \[\frac{1}{\sqrt{2}}{{({{i}_{i}}+{{i}_{2}})}^{2}}\] done clear
  C)
             \[\frac{1}{\sqrt{2}}{{(i_{1}^{2}+i_{2}^{2})}^{1/2}}\] done clear
  D)
             \[\frac{1}{2}{{(i_{1}^{2}+i_{2}^{2})}^{1/2}}\] done clear
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• question_answer24)
  In an ac circuit, the current is given by \[i=5\sin \,\left( 100\,t-\frac{\pi }{2} \right)\] and the ac potential is\[V=200\sin \,(100)\,volt.\] Then the power consumption is  [CBSE PMT 1995; MH CET 1999; CPMT 2002]
  A)
             20 watts                                  done clear
  B)
             40 watts done clear
  C)
             1000 watts                             done clear
  D)
             0 watt done clear
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• question_answer25)
  An electric lamp is connected to 220 V, 50 Hz supply. Then the peak value of voltage is [AFMC 1996]
  A)
             210 V                                        done clear
  B)
             211 V done clear
  C)
             311 V                                        done clear
  D)
             320 V done clear
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• question_answer26)
  In a circuit, the value of the alternating current is measured by hot wire ammeter as 10 ampere. Its peak value will be [MP PET 1996; AMU (Med.) 1999;  KCET (Engg./Med.) 2000; CPMT 2003]
  A)
             10 A                                          done clear
  B)
             20 A done clear
  C)
             14.14 A                                    done clear
  D)
             7.07 A done clear
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• question_answer27)
  The voltage of domestic ac is 220 volt. What does this represent                                               [MP PMT 1996]
  A)
             Mean voltage done clear
  B)
             Peak voltage done clear
  C)
             Root mean voltage done clear
  D)
             Root mean square voltage done clear
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• question_answer28)
  The r.m.s. voltage of domestic electricity supply is 220 volt . Electrical appliances should be designed to withstand an instantaneous voltage of
  A)
             220 V                                        done clear
  B)
             310 V done clear
  C)
             330 V                                        done clear
  D)
             440 V done clear
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• question_answer29)
  The process by which ac is converted into dc is known as                              [RPMT 1997]
  A)
             Purification                            done clear
  B)
             Amplification done clear
  C)
             Rectification                          done clear
  D)
             Current amplification done clear
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• question_answer30)
  In an ac circuit with voltage V and current I, the power dissipated is                                         [CBSE PMT 1997]
  A)
             VI done clear
  B)
             \[\frac{1}{2}VI\] done clear
  C)
             \[\frac{1}{\sqrt{2}}VI\] done clear
  D)
             Depends on the phase between V and I done clear
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• question_answer31)
  For an ac circuit \[V=15\sin \omega t\] and \[I=20\cos \omega t\] the average power consumed in this circuit is                    [RPET 1999]
  A)
             300 Watt                                 done clear
  B)
             150 Watt done clear
  C)
             75 Watt                                   done clear
  D)
             zero done clear
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• question_answer32)
  A bulb is connected first with dc and then ac of same voltage then it will shine brightly with         [RPET 2000]
  A)
             AC done clear
  B)
             DC done clear
  C)
             Brightness will be in ratio 1/1.4 done clear
  D)
             Equally with both done clear
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• question_answer33)
  An ac supply gives 30 V r.m.s. which passes through a 10\[\Omega \] resistance. The power dissipated in it is      [AMU (Med.) 2001]
  A)
             \[90\sqrt{2}\,W\]                done clear
  B)
             \[90\,W\] done clear
  C)
             \[45\sqrt{2}\,W\]                done clear
  D)
             \[45\,W\] done clear
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• question_answer34)
  The frequency of an alternating voltage is 50 cycles/sec and its amplitude is 120V. Then the r.m.s. value of voltage is  [BHU 1999; MH CET (Med.) 2001; KCET (Med.) 2001; MH CET 2003]
  A)
             101.3V                                     done clear
  B)
             84.8V done clear
  C)
             70.7V                                        done clear
  D)
             56.5V done clear
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• question_answer35)
  A resistance of 20 ohms is connected to a source of an alternating potential \[V=220\sin (100\pi t)\]. The time taken by the current to change from its peak value to r.m.s value is  [MP PET 2001]
  A)
             0.2 sec                                      done clear
  B)
             0.25 sec done clear
  C)
             \[25\times {{10}^{-3}}\]sec     done clear
  D)
             \[2.5\times {{10}^{-3}}\]sec done clear
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• question_answer36)
  Voltage and current in an ac circuit are given by \[V=5\sin \,\left( 100\pi t-\frac{\pi }{6} \right)\] and \[I=4\sin \,\left( 100\pi t+\frac{\pi }{6} \right)\] [Kerala PET 2001]
  A)
             Voltage leads the current by \[{{30}^{o}}\] done clear
  B)
             Current leads the voltage by \[{{30}^{o}}\] done clear
  C)
             Current leads the voltage by \[{{60}^{o}}\] done clear
  D)
             Voltage leads the current by \[{{60}^{o}}\] done clear
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• question_answer37)
  If an ac main supply is given to be 220 V. What would be the average e.m.f. during a positive half cycle [MH CET 2002]
  A)
             198V                                         done clear
  B)
             386V done clear
  C)
             256V                                         done clear
  D)
             None of these done clear
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• question_answer38)
  In an ac circuit, the r.m.s. value of current, Irms is related to the peak current, I0 by the relation [AFMC 2002]
  A)
             \[{{I}_{rms}}=\frac{1}{\pi }{{I}_{0}}\]                             done clear
  B)
             \[{{I}_{rms}}=\frac{1}{\sqrt{2}}{{I}_{0}}\] done clear
  C)
             \[{{I}_{rms}}=\sqrt{2}{{I}_{0}}\]                                       done clear
  D)
             \[{{I}_{rms}}=\pi {{I}_{0}}\] done clear
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• question_answer39)
  An alternating voltage is represented as \[E=20\sin 300t.\] The average value of voltage over one cycle will be [MP PMT 2002]
  A)
             Zero                                          done clear
  B)
             10 volt done clear
  C)
             \[20\sqrt{2}\] volt               done clear
  D)
             \[\frac{20}{\sqrt{2}}\] volt done clear
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• question_answer40)
  The ratio of peak value and r.m.s value of an alternating current is                                           [MP PMT 2002]
  A)
             1     done clear
  B)
             \[\frac{1}{2}\] done clear
  C)
             \[\sqrt{2}\]                            done clear
  D)
             \[1/\sqrt{2}\] done clear
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• question_answer41)
  A 280 ohm electric bulb is connected to 200V electric line. The peak value of current in the bulb will be [MP PET 2002]
  A)
             About one ampere            done clear
  B)
             Zero done clear
  C)
             About two ampere            done clear
  D)
             About four ampere done clear
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• question_answer42)
  An ac source is rated at 220V, 50 Hz. The time taken for voltage to change from its peak value to zero is [Orissa JEE 2003]
  A)
             50 sec                                       done clear
  B)
             0.02 sec done clear
  C)
             5 sec                                         done clear
  D)
             \[5\times {{10}^{-3}}\] sec done clear
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• question_answer43)
  If the value of potential in an ac, circuit is 10V, then the peak value of potential is                                              [CPMT 2003]
  A)
             \[\frac{10}{\sqrt{2}}\]       done clear
  B)
             \[10\sqrt{2}\] done clear
  C)
             \[20\sqrt{2}\]                       done clear
  D)
             \[\frac{20}{\sqrt{2}}\] done clear
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• question_answer44)
  A lamp consumes only 50% of peak power in an a.c. circuit. What is the phase difference between the applied voltage and the circuit current                                            [MP PMT 2004]
  A)
             \[\frac{\pi }{6}\]                  done clear
  B)
             \[\frac{\pi }{3}\] done clear
  C)
             \[\frac{\pi }{4}\]                  done clear
  D)
             \[\frac{\pi }{2}\] done clear
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• question_answer45)
  If an alternating voltage is represented as            \[E=141\sin (628\,t),\] then the rms value of the voltage and the frequency are respectively           [Kerala PET 2005]
  A)
             \[141V,\,628Hz\]                 done clear
  B)
             \[100V,\,50Hz\]                   done clear
  C)
             \[100V,\,100Hz\]                 done clear
  D)
             \[141V,\,\,100Hz\] done clear
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• question_answer46)
  The maximum value of a.c. voltage in a circuit is 707V. Its rms value is                                      [MP PET  2005]
  A)
             70.7 V                                       done clear
  B)
             100 V                                        done clear
  C)
             500 V                                        done clear
  D)
             707 V done clear
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