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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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