Alternating Current Mcqs
This set of Multiple choice questions and answers focuses on study of Alternating Current in Physics. These questions are chosen from a collection of most authoritative and best reference books on Physics. Our aim is to prepare an individual for competitive exams like NTS, GAT, ECAT, MDCAT, Teaching jobs Tests and Chemical industry job interviews. One should practice our Mcqs to assimilate knowledge on Alternating Current in Physics comprehensively.
2. A 10? electric heater is connected to a 220V 50Hz mains supply. What is the peak value of the potential difference across the heater element?
220V
220/ ??2V
110V
220 ??2V
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3. A capacitor of capacitance 30?F is charged by a constant current of 10mA. If initially the capacitor was uncharged what is the time taken for the potential difference across the capacitor to reach 300V?
0.9sec
15 sec
1.5x105sec
0.9x102sec
4. A changing magnetic flux produces around itself an induced
Magnetic field
Electric field
Electromagnetic force
Artificial gravitational field
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5. A choke is used as a resistance in
DC circuit
AC circuits
Both AC and DC circuit
Full wave rectifier circuit
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6. A pure variable resistor is connected in series with a pure capacitor of fixed capacitance. The impedance of the circuit
Remains
Becomes infinite
Becomes zero
Increases
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7. a voltage V = V? cos ?t is applied across a resistor of resistance R the average power dissipated per cycle in the resistor is given by
V?/?2R
V?/?2?R
V?2/?2R
V?2/?2?R
8. A wire of resistance R is coiled inductively so that its inductance is L. The impedance of the coil at a frequency of f is
(R+2?fL)
R+1/2?fL
(R2+f2L2)
(R2+4?2f2L2)
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9. Ammeter connected in an AC circuit measures
Exact value of current
Rms value of current
Net value of current
Peak value of current
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10. An A.C series circuit containing 4? resistance and 3-? inductive reactance. The impedance of the circuit is
1?
5?
7?
7/?2?
11. An alternating current is represented by the equation I = I?sin?t which of the following equation represents an alternating current of frequency and amplitude twice that of the above current?
I = 2I?Sin(?t/2)
I = 2I?Sin(2?t)
I = 2ISin?t
I = I?sin(2?t)
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12. An alternating current of r.m.s value of 2A and a steady direct current I flowing through identical resistors dissipate heat at the same rate. What is the current I?
2A
A
13. An alternating current of r.m.s value of 4.0 A and frequency 50Hz flows in a circuit containing 10? resistor. The peak current is then
20A
20.66A
6.66A
5.66A
14. An alternating current or voltage
Fluctuates off and on
Varies in magnitude alone
Changes its direction again and again
Changes its magnitude harmonically and reverses its direction of flow after regularly recurring intervals.
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15. An alternating potential difference is connected across a pure resistor and the frequency of the supply is varied but the rms value of the voltage is kept constant. The mean rate of heat dissipated from the resistor is
Directly proportional to f
Directly proportional to ??f
Directly proportional to f2
Inversely proportional to f
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