“12th Class Physics Chapter 16 Quiz: Alternating Current” introduces the very concept of alternating current (AC) in students, which is a type of current they use in homes, industry, and power distribution systems. This chapter is very important for MDCAT students, as it builds up a very strong foundation regarding the transmission of electrical energy over long distances. Our MDCAT Quizzes on this chapter will surely test your knowledge and prepare you for examination questions based on alternating current.
Overview of Alternating Current
Alternating current (AC) is different from direct current (DC) because it periodically reverses direction. This chapter opens with a description of the most basic characteristics: amplitude, frequency, and phase of AC. The frequency measured in hertz (Hz) refers to the number of times the current changes direction per second. Students are expected to know the peak value of an alternating current—maximum current—and the rms value of the current, which gives the effective value of the current with regard to its heating effect. The relationship between the peak value and the rms value is obtained and the concept of phase difference in AC circuits is introduced.
AC Circuits
The chapter continues with a detailed explanation of AC circuits, which may include resistors, inductors, and capacitors. In a purely resistive AC circuit, the current and voltage are in phase; that is, they reach their maximum values at the same time. However, in circuits containing inductors and capacitors, the current and voltage are out of phase. Inductive reactance and capacitive reactance are introduced, explaining how inductors and capacitors oppose changes in current. Students will learn how to calculate the total impedance in an AC circuit, which is the combined opposition of resistance and reactance. The concept of resonance in an RLC (resistor, inductor, capacitor) circuit is also covered, explaining how resonance occurs when the inductive reactance and capacitive reactance cancel each other out.
Power in AC Circuits
This will become crucial in dealing with power in AC circuits for practical applications in power generation and transmission. In the chapter on average power and instantaneous power in an AC circuit, power fluctuates as current and voltage change directions. The concept of the power factor is treated thoroughly since it is defined as the ratio between real power to apparent power. When the power factor equals 1 or 100%, then all energy supplied to the circuit is fully utilized; otherwise, there is inefficiency involved. Students shall be able to determine the power consumed in an AC circuit and how the power factor enters into the consumption of energy.
Transformers and Power Transmission
This is, in fact, the major use of alternating current, using transformers to change voltage levels for transfer over long distances. In this chapter, you shall learn the details of how it works by the principle of electromagnetic induction. It consists of two coils: one, called the primary, where the voltage comes in, and the other, called the secondary, where the output voltage is obtained. The change of voltage depends upon the turns ratio of the coils. You shall learn about step-up and step-down transformers and how they are applied in the long-distance transmission of power.
MDCAT Quiz: Test Your Knowledge of Alternating Current
The MDCAT Quiz of Chapter 16 pertains to some critical subjects like AC circuits, resonance, power in AC circuits, impedance, and how a transformer works. This will assess your understanding and help you judge how best you have been prepared to take on MDCAT questions about alternating current.
- Test Name: 12th Class Physics Chapter 16 Quiz
- Type: Quiz Test
- Total Questions: 30
- Total Marks: 30
- Time: 30 minutes
Note: Answer of the questions will change randomly each time you start the test, once you are finished, click the View Results button.
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Free Flashcards for Alternating Current
For quick revision, use free flashcards for Chapter 16. These flashcards cover important topics such as AC circuits, power in AC circuits, impedance, transformers, and resonance. Flashcards are a very effective tool for reinforcing key concepts and formulas so that they become easier to recall during your MDCAT preparation.
What is the frequency of AC commonly expressed in?
Hertz
What type of current periodically changes direction?
Alternating current
What is the phase difference between voltage and current in a purely resistive-capacitive-inductive AC circuit?
Zero degrees
What is the unit of apparent power?
Volt-ampere
What is the characteristic of an AC waveform that determines its rate of change?
Frequency
What is the relationship between peak-to-peak value and RMS value for an AC waveform?
Peak-to-peak value times square root of 2
What is the phase difference between voltage and current in a purely capacitive-inductive AC circuit?
Zero degrees
What is the unit of reactive power?
Volt-ampere reactive
What is the characteristic of an AC waveform that determines its time taken to complete one cycle?
Period
What is the relationship between peak value and RMS value for an AC waveform?
Peak value times square root of 2
What is the phase difference between voltage and current in a purely resistive-inductive-capacitive AC circuit?
Zero degrees
What is the unit of angular frequency?
Radians per second
What is the characteristic of an AC waveform that determines its displacement from the zero point?
Amplitude
What is the relationship between frequency and angular frequency for an AC waveform?
Directly proportional
What is the phase difference between voltage and current in a purely resistive-capacitive AC circuit?
Less than 90 degrees
What is the unit of peak-to-peak voltage?
Volts
What is the characteristic of an AC waveform that determines the number of cycles per second?
Frequency
What is the relationship between frequency and wavelength for an AC waveform?
Inversely proportional
What is the phase difference between voltage and current in a purely capacitive-inductive AC circuit?
Less than 90 degrees
What is the unit of peak voltage?
Volts
What is the characteristic of an AC waveform that determines its intensity?
Amplitude
What is the phase difference between voltage and current in a purely resistive-inductive AC circuit?
Less than 90 degrees
What is the relationship between frequency and time period for an AC waveform?
Inversely proportional
What is the peak-to-peak value of an AC waveform?
Twice the peak value
What is the instrument used to measure resistance in an AC circuit?
Ohmmeter
What is the unit of frequency?
Hertz
What is the average power consumed in a purely resistive AC circuit?
Voltage times current
What is the period of a 60 Hz alternating current?
1/60 second
What is the phase difference between voltage and current in a purely capacitive AC circuit?
90 degrees
What is the frequency of a 50 Hz alternating current?
50 cycles per second
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