Class 12 Physics Alternating Currents Notes and Important Questions
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Notes for Class 12 Alternating Currents (Physics) are shown above.
Practice
Important Questions
In the given figure, an inductor of inductance L, a capacitor of capacitance C, a resistor of resistance R are connected in series and the combination is then connected to an alternating source of emf.
Draw a phase diagram for the circuit.
Calculate impedance of the circuit.
If L = 0.5 H and C = 20 μF, find the resonant frequency of the circuit.
Give an application of resonating a.c. circuit.
Why is 220 V a.c. more dangerous than 220 V d.c.? Explain.
Define root mean square value of AC.
The given figure shows the LCR series circuit.
i) Obtain the expression for impedance of the circuit.
ii) What is resonance in LCR series circuit?
iii) Calculate the resonant frequency.
iv) What is quality factor of the circuit?
Define root mean square value of ac.
The given figure shows the LCR series circuit.
Obtain the expression for impedance of the circuit.
What is resonance in LCR series circuit?
Calculate the resonant frequency.
What is quality factor of the circuit?
Define impedance of LCR circuit.
A series LCR circuit is given in figure.
Calculate the impedance of the circuit if
L = 60 mH, C = 0.50 μF and R = 300 Ω.
How does resonance occur in above LCR circuit? Write the required expression.
A device is connected across an ac source of voltage V = V₀ sinωt and the current through X is given by:
I = I₀ sin(ωt + π/2)
Identify, which device is X? Also, write the expression for its reactance.
Draw graphs showing the variation of voltage and current with time over one cycle of an alternating current for X.
In our country Nepal, the supply ac voltage is 220 V. The peak value of voltage is about
110 V
220 V
310 V
350 V
An AC generator produces a voltage of peak value V. The frequency of rotation of the coil of the generator is f. The rms value of the voltage produced is
V / 2√2
V / √2
V√2
2V√2
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Exam
Past Question Analysis
Historical exam-pattern data from past NEB question papers — not a prediction of future questions.
4
Question Items
2
Total Marks
3
Papers Appeared In
| Year | Question Items | Marks |
|---|---|---|
| 2083 | 1 | 1 |
| 2082 | 2 | — |
| 2081 | 1 | 1 |
Also appears in 5 model questions (not counted above — model sets aren't actual NEB exam history).
Alternating Currents introduces electrical quantities that change periodically with time. Students study RMS values, AC circuits containing resistors, capacitors and inductors, phasors, impedance, resonance, power and power factor.
This page covers Alternating Currents, chapter 19 of 25 in the Class 12 Physics syllabus set by the National Examination Board (NEB). 10 important questions for this chapter are available, each with a full solution.
For numerical and derivation-based chapters like this one, working through past NEB questions is usually more useful than re-reading notes alone — try solving each important question above before checking the solution, then compare your working step by step.