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WorksheetsAlternating Current
Total questions: 20
Worksheet time: 3600secs
The power is transmitted from a power house on high voltage ac because...
Electric current travels faster at higher volts
It is more economical due to less power wastage
It is difficult to generate power at low voltage
Chances of stealing transmission lines are minimized
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 wt volts and I = 2 sin wt amperes (where w = 2pf). The power dissipated in the instrument is
Zero
10W
5W
2.5W
In an ac circuit, V and I are given by V = 100 sin (100 t) volts,
104 watt
10 watt
2.5 watt
5 watt
Alternating current can not be measured by dc ammeter because
ac cannot pass through dc ammeter
Average value of complete cycle is zero
ac is virtual
ac changes its direction
The resistance of a coil for dc is in ohms. In ac, the resistance
Will remain same
Will increase
Will decrease
Will be zero
If instantaneous current is given by
4 amperes
22 amperes
42 amperes
Zero amperes
In an ac circuit, peak value of voltage is 423 volts. Its effective voltage is...
400 volts
323 volts
300 volts
340 volts
A generator produces a voltage that is given by
60 Hz and 240 V
19 Hz and 120 V
19 Hz and 170 V
754 Hz and 70 V
The power factor of LCR circuit at resonance is...
0.707
1
Zero
0.5
An inductance of 1 mH a condenser of 10 mF and a resistance of 50 W are connected in series. The reactances of inductor and condensers are same. The reactance of either of them will be...
100 W
30 W
3.2 W
10 W
The natural frequency of a L-C circuit is equal to...
2π1 LC
2π LC1
2π1 CL
2π1 LC
An ac circuit consists of an inductor of inductance 0.5 H and a capacitor of capacitance 8 mF in series. The current in the circuit is maximum when the angular frequency of ac source is
500 rad/sec
2 x 105 rad/sec
4000 rad/sec
5000 rad/sec
In a region of uniform magnetic induction B=10−2 tesla, a circular coil of radius 30 cm and resistance π2 ohm is rotated about an axis which is perpendicular to the direction of B and which forms a diameter of the coil. If the coil rotates at 200 rpm the amplitude of the alternating current induced in the coil is
4 π2 mA
30 mA
6 mA
200 mA
An inductive circuit contains a resistance of 10 ohm and an inductance of 2.0 henry. If an ac voltage of 120 volt and frequency of 60 Hz is applied to this circuit, the current in the circuit would be nearly
0.32 amp
0.16 amp
0.48 amp
0.80 amp
In a LCR circuit having L = 8.0 henry, C = 0.5 mF and R = 100 ohm in series. The resonance frequency in per second is
600 radian
600 Hz
500 radian
500 Hz
In LCR circuit, the capacitance is changed from C to 4C. For the same resonant frequency, the inductance should be changed from L to...
2L
L / 2
L / 4
4L
A 120 volt ac source is connected across a pure inductor of inductance 0.70 henry. If the frequency of the source is 60 Hz, the current passing through the inductor is...
4.55 amps
0.355 amps
0.455 amps
3.55 amps
The impedance of a circuit consists of 3 ohm resistance and 4 ohm reactance. The power factor of the circuit is...
0.4
0.6
0.8
1.0
The power factor of a good choke coil is...
Nearly zero
Exactly zero
Nearly one
Exactly one
An alternating current source of frequency 100 Hz is joined to a combination of a resistance, a capacitance and a coil in series. The potential difference across the coil, the resistance and the capacitor is 46, 8 and 40 volt respectively. The electromotive force of alternating current source in volt is...
94
14
10
76
