Alternating Current - Quiz 7

ALTERNATING CURRENT QUIZ-7

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 ac is given by equation I=I₁ cos⁡ωt+I₂ sin⁡ωt. The rms value of current is given by

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Solution

Q2. A resistance of 20 Ω is connected to a source of an alternating potential V=220 sin⁡(100 πt). The time taken by the current to change from the peak value to rms value, is

•  0.2 s
•  0.25 s
•  7.5×10^(-3) C
•  2.5×10^(-3) C

Solution

Q3. In the circuit given in Fig V_C=50 V and R=50 Ω. The values of C and V_R are

•  3.3 mF,60 V
•  104 μF,98 V
•  52 μF,98 V
•  2 μF,60 V

Solution

Q4. In a black box of unknown elements (L or R or any other combination), an ac voltage E=E₀ sin⁡(ωt+ϕ) is applied and current in the circuit was found to be I=I₀ sin⁡[ωt+ϕ+(π/4)]. Then the unknown elements in the box may be?

•  Only capacitor
•  Inductor and resistor both
•  Either capacitor, resistor and inductor or only capacitor and resistor
•  Only resistor

Solution

Q5. If a direct current of value a ampere is superimposed on an alternative current I=b sin⁡ωt flowing through a wire, what is the effective value of the resulting current in the circuit?

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Solution

Q6. In the circuit shown in Fig, the rims currents I₁,I₂ and I₃ are altered by varying the frequency f of the oscillator. The output voltage of the oscillator remains sinusoidal and has a fixed amplitude. Which curves in figure correctly indicate the variation with frequency of the currents I₁,I₂,and I₃?

•  Q Q Q
•  R Q Q
•  Q P R
•  Q R P

Solution

Q7. A sinusoidal alternating current of peak value I₀ passes through a heater of resistance R. What is the mean power output of the heater?

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Solution

Q8. In the above question, the capacitive reactance in the circuit is

•  100 Ω
•  25 Ω
•  √(125×75) Ω/span>
•  400 Ω

Solution

Q9. An ideal choke takes a current of 10 A when connected to an ac supply of 125 V and 50 Hz. A pure resistor under the same conditions takes a current of 12.5 A. If the two are connected to an ac supply of 100 V and 40 Hz, then the current in series combination of above resistor and inductor is

•  10/√2 A
•  12.5 A
•  20 A
•  10 A

Solution

Q10. Current in an ac circuit is given by I=3 sin⁡ωt+4 cos⁡ωt, then

•  rms value of current is 5 A
•  Mean value of this current in any one half period will be 6/π
•  If voltage applied is V=V_m sin⁡ωt, then the circuit may be containing resistance and capacitance only
•  If voltage applied is V=V_m sin⁡ωt, the circuit may contain resistance and inductace only

Solution