# Alternating Current -Important Questions & Preparation Tips

In this article you will get the clue that from where and how the questions are being framed from chapter Alternating Current

CBSE Class 12^{th} physics chapter, **Alternating Current** obtains 04 Marks. Experts of **Jagranjosh.com** offer the best practice material that covers all important questions so that students will not miss any portion while preparing for board exams or competitive exams. Consider the mentioned terms/questions at the time of studying.

- Find the value of current flowing through the resistor connected with an alternating voltage source?
- Explain why average current is zero in one complete cycle when connected to an a.c. source whereas average power is not zero?
- What is the usefulness of the rms concept?
- What would happen if the household appliances are supplied with the peak voltage more than 311 V?
- Define phasor and phasor diagram?
- Deduce the expression for current when an ac voltage is applied to an inductor?
- How is the inductive reactance different from that of resistance?
- Show that the average power supplied to an inductor over one complete cycle is zero?
- Deduce the expression for current when an ac voltage is applied to a capacitor?
- How is the inductive reactance different from that of capacitive reactance?
- Explain the phasor diagram solution for the LCR circuit?
- What are the disadvantages of using phasor diagram for LCR circuits?
- Provide with an analytical solution for the LCR circuit?
- Define wattles circuit and name the circuits which are wattles
- Formula for average power dissipation
- Differentiate between natural frequency and resonant frequency?
- How is resonance useful in tuning of radio channels?
- Deduce the sharpness and quality factor in an ac circuit?
- Give the average power dissipated in an ac circuit? Also discuss the various cases.

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- What is principle on which the metal detector works?
- Deduce the total energy in an LC Circuit?
- How is LC oscillation similar to the oscillation of attached springs?
- What are the similarities between forced oscillations and driven LCR circuit?
- Differentiate between step-up and step down transformer?
- What kind of losses occurs in an actual transformer?
- Explain with a phasor diagram, the differences between a resistor, an inductor and a capacitor?

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- Why is sparking observed when an electric appliance is suddenly switched off?
- A 60V, 10W lamp is to be used on AC source of 100V,60Hz. Calculate the inductance of the choke coil required to be put in series to run the lamp[. How much pure resistance should be used in place of the choke coil, so that the lamp may run on its rated voltage?
- An AC source is connected to two circuits, as shown. Obtain the current through the resistance R at resonance in both the circuits?

- How much current is drawn by the primary of a transformer which steps down 220V to 22V to operate a device having an impedance of 220Ώ?
- Why is inductance more appropriate than a resistance to decrease alternating current?
- A bulb and a capacitor are connected in series to a source of alternating current. What will happen on increasing the frequency of the current?
- Why is it not possible to have electrolysis by AC?
- What is the main advantage of AC over DC due to which AC is used?
- How will you use a 100V, 50W bulb on 200V AC mains?
- I=I
_{0}e^{-t/T}is the output current in a circuit where

e= exponential

t= time

I_{0}= peak current

T=period, then find the average current

- For V= 200 sin 100 л t. Find time after which voltage raise to RMS value from zero

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