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# Test C - Alternating Current (AC) Assignment Class 12 Notes | EduRev

## Class 12 : Test C - Alternating Current (AC) Assignment Class 12 Notes | EduRev

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1. Why we prefer a choke coil to a rheostat in controlling a.c. 
2. A bulb connected in series with solenoid is lit by an a.c. source. If a soft iron core is introduced in the
solenoid, will the bulb glow brighter ? 
3. Sketch a graph to show the variation of inductive reactance with frquency. 
4. The resistance of a coil is 10 ? for direct current. When an alternating current is passed through the coil,
will the opposition remains the same ? Explain. 
5. A person carrying anything of metal when passes through a metal detector emits a sound. On what principle
does this detector work ? 
6. A coil having a resistance of 60 ? and inductance of 0.500 H, connected to an a.c. source of
110 volt, 50 cycles/sec. Find the rms value of current in the circuit. 
7. A coil has a resistance of 10 ? and inductance of 0.4 H. It is connected to an a.c. source of 6.5 V ,
90/ ? Hz. Find the average power consumed in the circuit. 
8. Prove that the phase difference between voltage, and current in an a.c. circuit containing only capacitor is
?/2. 
9. The instantaneous voltage is given by E = 140 sin 300 t. What is
(i) peak current  (ii) rms current and (iii) frequency of the supply.
When connected to 10 ? resistance. 
10. A pure inductor of self induction 1 H. is connected across an alternating voltage of 115 V and frequency
60 Hz. Calculate (i) inductive reactance (ii) effective current (iii) peak current
(iv) average power. 
11. Prove that energy remains conserved when a charge oscillates in a.c. circuit. 
12. Draw a phasor diagram of LCR series circuit and find expression for impedance and phase
difference. 
13. An inductor 200 mH, capacitor 500 µF, resistor 10 ? are connected in series with a 100 V , variable
frequency ac source. Calculate the
(i) frequency at which the power factor of the circuit is unity.
(ii) current amplitue at this frquency.
(iii) Q-factor. 
ALTERNATING CURRENT T E S T - C
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