Alternating Current-Quiz 1

ALTERNATING CURRENT QUIZ-1

Dear Readers,

JEE Advanced Physics Syllabus can be referred by the IIT aspirants to get a detailed list of all topics that are important in cracking the entrance examination. JEE Advanced syllabus for Physics has been designed in such a way that it offers very practical and application-based learning to further make it easier for students to understand every concept or topic by correlating it with day-to-day experiences. In comparison to the other two subjects, the syllabus of JEE Advanced for physics is developed in such a way so as to test the deep understanding and application of concepts.

Q1. An inductive coil has a resistance of 100 Ω. When an ac signal of frequency 1000 Hz is fed to the coil, the applied voltage leads the current by 45°. What is the inductance of the coil?

•  2 mH
•  3.3 mH
•  16 mH
•  √5 mH

Solution

Q2. Fig shows a source of alternating voltage connected to a capacitor and a resistor. Which of the following phasor diagrams correctly describes the phase relationship between I_C, the current between the source and the capacitor, and I_R, the current in the resistor?

•  
  
•  
  
•  
  
•  
  

Solution

(a) Since the capacitor is connected in series to the resistor, current I_C from the supply and I_R through the resistor is in phase as represented by choice (a)

Q3. Determine the RMS value of a semi-circular current wave which has a maximum value of a

•   (1/√2)a
•  √((3/2)) a
•  √((2/3)) a
•  (1/√3)a

Solution

Q4. The value of current in two series LCR circuits at resonance is the same. Then

•  Both circuits must be having the same value of capacitance and inductance
•  In both circuits ratio of L and C will be the same
•  For both the circuits X_L/X_Cmust be the same at that frequency
•  Both circuits must have the same impedance at all frequencies

Solution
(c) X_L=X_C at resonance
X_L/X_C =1 for both circuits
Impedance may be different if the applied voltage is different

Q5. AnLCR circuit contains resistance of 100 Ω and a supply of 200 V at 300 rad angular frequency. If the only capacitance is taken out from the circuit and the rest of the circuit is joined, current lags behind the voltage by 60°. If, on the other hand, only the inductor is taken out the current leads by 60° with the applied voltage. The current flowing in the circuit is

•  1 A
•  1.5 A
•  2 A
•  2.5 A

Solution

Q6. Which voltmeter will give zero reading at resonance?

•  V₁
•  V₂
•  V₃
•  None

Solution

(b) At resonance, the series combination of L and C gives zero impedance. At resonance, the voltage across L and C are equal but opposite in phase

Q7. In the series LCR circuit, the voltmeter and ammeter readings are:

•  V=100 V,I=2 A
•  V=100 V,I=5 A
•  V=1000 V,I=2 A
•  V=300 V,I=1 A

Solution

Q8. A capacitor of capacitance 1 μF is charged to a potential of 1V. It is connected in parallel to an inductor of inductance 10^-3 H. The maximum current that will flow in the circuit has the value

•  √1000 mA
•  1 mA
•  1 μA
•  1000 mA

Solution

Q9. A resistor and a capacitor are connected to an ac supply of 200 V, 50 Hz in series. The current in the circuit is 2 A. If the power consumed in the circuit is 100 W then the resistance in the circuit is

•  100 Ω
•  25 Ω
•  √(125×75) Ω
•  400 Ω

Solution

Q10. When an AC source of emf e=E₀sin⁡(100t) is connected across a circuit, the phase difference between the emf e and the current i in the circuit is observed to be π/4 , as shown in the diagram. If the circuit consists possibly only of R – C or R – L or L – C in series, find the relationship between the two elements

•  R=1 k Ω,C=10 μF
•  R=1 k Ω,C=1 μF
•  R=1 k Ω,L=10 H
• R=1 k Ω,L=1 H

Solution