Physics Chapter 5 – Alternating Current (Class 12) for FSC, Entry Tests & NTS Preparation
Chapter 5, Alternating Current, is an important topic for Class 12 students preparing for FSC board exams and engineering entry tests like ECAT, NUST, and FAST, as well as NTS exams. This chapter explains the generation, characteristics, and behavior of alternating current (AC) in electrical circuits. Understanding AC is essential for studying electrical power systems, electronics, and practical applications in homes and industries.
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The principle of an AC generator is.
NTS 2019
Physics
Alternating Current
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The ripple factor of a half-wave rectifier is:
PMC Practice 2
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Alternating Current
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In which rectifier is the ripple factor less?
PMC Practice 1
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In a step up transformer ________.
NTS 2019
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Identify the factor on which mutual inductance does not depend:
PMC Practice 3
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Impedance in RLC series circuit Is given by
Wavelength of X-rays is of the order of?
Mutual inductance has a practical role in performance of:
PMC Practice 4
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For an ideal step-up transformer Ps ——- Pp.
PMC Practice 8
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Transformer is used in rectification to ___________ the supply voltage.
PMC Practice 5
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Impedance of a circuit Is calculated as:
The maximum instantaneous value measured from zero value is known as?
PMC Sample 3
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Current that fluctuates periodically with time is ——
PMC Practice 4
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In a step-down transformer, the current in the primary coil is ______ than that in the secondary coil.
PMC 2021 Tested
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Resistance of RCL series circuit at resonance Is?
In a practical transformer mutual induction between primary and secondary coils takes place. In such transformer what can be deduced about the power.
UHS 2018
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Alternating Current
Work, Power & Energy
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If an AC voltage of rms value of 10 volts is applied as input of a half-wave rectifier, then the voltage value of the DC output will be:
PMC Practice 4
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An alternation voltage V (in volts) is represented by the equation:
V = 300 sin (100πt)
What is the value of “f” for this voltage?
UHS 2019
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Alternating Current Generators use:
PMC Practice 5
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Simple oscillating circuit consists of?
The process of combining low frequency waves with high frequency is called:
Voltage Is current In RC circuit.
The bridge rectifier is preferred to an ordinary two diode full-wave rectifier because?
PMC Practice 2
Physics
Alternating Current
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What is the instantaneous power dissipated through a resistor of resistance 10 ohm if it is connected to an AC source of frequency 15 Hz at 1/180 sec if peak value is 20 V?
UHS 2018
Physics
Alternating Current
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If the peak voltage is 9V, calculate the peak to peak voltage.
PMC Practice 8
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Power factor of the pure capacitive circuit is?
The number of diodes in bridge rectifier is
PMC Sample 3
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Step up transformer have ________ turns in secondary coil.
PMC Practice 1
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The AC generator is similar to:
PMC 2021 Tested
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What is the range of typical band gap in conductors
PMC Sample 3
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If the instantaneous current in a circuit is given by I = A sin (wt) ampere, the RMS value of the current is:
PMC Practice 3
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The direction of current through the load resistance of a full-wave rectification circuit:
UHS 2019
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P = Irms Vrms Is applicable for
Half wave voltage multipliers can provide what degree of voltage multiplication?
PMC Practice 4
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An alternating voltage source is connected to a resistor R, and a capacitor C, then which of the following statements about phase angle between voltage V and current I is correct?
NUMS 2019 Cancelled
Physics
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In a bridge type full-wave rectifier, if Vm is the peak voltage across the secondary coil of the transformer, the maximum voltage coming across each reverse biased diode is:
PMC Practice 5
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Power of RCL circuit at resonance Is?
A diode works in _______ bias for rectification.
PMC Practice 6
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At resonance, the RLC circuit behaves like:
If a half wave rectifier is used to convert 50Hz AC into DC, then the number of pulses present in rectified voltage is:
PMC Sample 1
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If a half-wave rectifier is used to convert 50 Hz AC into DC, then the number of pulses present in the rectifier voltage is:
PMC Practice 2
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An Inductor of 1H Is connected across a 220V, 50Hz supply. The peak value of current is approximately:
Reactance of an Inductor Is given by:
Electromagnetic waves are produced due to flow of
Which of the following remains unchanged in a transformer.
PMC Sample 3
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In a pure resistive circuit current and voltage are
Consider two capacitors with capacitance 2µF and 4µF. With which type of connection will the 4µF capacitor have a greater amount of stored energy than the 2µF capacitor?
PMC Practice 2
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RLC circuit can be excited by
Which of the following are component of half wave rectifier?
PMC Practice 1
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Which of the following color has the highest energy?
X-rays have frequency greater than
The principle of a capacitor is based on which of the following facts?
NTS 2011
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A circuit that adds positive or negative D.C. voltage to an input sine wave is called:
PMC Practice 4
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A half wave rectifier is operating from 50 Hz mains, fundamental frequency of ripple will be
PMC Sample 3
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Power factor. of RLC circuit at Resonance Is
The output voltage of a rectifier is:
PMC Practice 4
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Voltage after which in forward bias current start to rise with increase in voltage is called:
PMC Sample 3
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The frequency of applied AC is 2 kHz. Its time period will be:
PMC Practice 3
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The use of a capacitor filter in a rectifier circuit gives satisfactory performance only when the load:
PMC Practice 3
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The angle made by the coil of an AC generator at a time Interval 3T/4 is?
The maximum efficiency of a half-wave rectifier is:
PMC Practice 3
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PIV stands for :
PMC 2020
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In case of half wave rectification the resistance of diode during negative half of A.C is:
UHS 2018
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Power factor in an AC circuit Is?
The frequency of AC used in Pakistan is
In RLC series circuit at resonance, the A.C voltage across Resistance R, Inductance L and capacitance C are 5V, 10V and 10 V respectively. The A.C voltage applied to the circuit will be:
NUMS 2015
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In electronic circuits, a PN junction diode is used to convert alternating current into direct current. This process is called:
NTS 2018
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Alternating Current
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In a full-wave rectification, the number of diodes used are:
PMC 2020
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The rectifier is a device which converts?
PMC Practice 3
Physics
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A full wave rectifier is operating from 50 Hz mains. Fundamental frequency of ripple will be:
PMC Practice 1
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Alternating Current
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What will be the Impedance for V = 10 sin(wt) and I = 20 sln(wt)
In a half wave rectifier, the diode conducts during:
NUMS 2019 Reconduct
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that the supply for the potentiometer is taken?
PMC Practice 8
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Key Concepts about Alternating Current
The chapter explains AC voltage and current, peak and RMS values, and the concept of phase difference. It covers AC in resistive, inductive, and capacitive circuits, including series and parallel combinations. The chapter also discusses impedance, power in AC circuits, resonance, and the use of AC in transformers and power distribution. Each concept is explained with diagrams, examples, and step-by-step problem-solving methods. These concepts are highly important for FSC board exams and engineering entry tests like ECAT, NUST, and FAST.
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Mastery of alternating current helps students understand AC circuits, solve numerical problems, and apply concepts to electrical devices and power systems. PLS Academy provides practice questions, solved past papers, and chapter-wise MCQs to help students revise these topics effectively. Regular study of this chapter improves problem-solving skills, conceptual clarity, and exam performance, ensuring students are well-prepared for FSC board exams, competitive entry tests, and NTS exams.
JazakAllah.
