Difference Between AM, FM, and PM for JEE Main 2025

Understanding the difference between Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM) is important in physics for JEE Main 2025. AM, FM, and PM are methods used to encode information in radio signals by varying different properties of a carrier wave.

Each modulation type has distinct advantages and applications, making them essential for JEE aspirants to understand. This page will help you distinguish between amplitude modulation and frequency modulation. Also, you will get to learn the difference between FM, AM, and PM modulation in tabular form.

How does FM Work?

In FM, a radio wave known as the "carrier" or "carrier wave" is modulated in frequency by the signal that is to be transmitted. However, the amplitude and the phase constant remain constant in the case of frequency modulation. Amplitude modulation or AM is a technique that we use in electronic communication, most commonly for transmitting information through a radio carrier wave.

Additionally, there is a term that is one of the two principal forms of angle modulation alongside frequency modulation, and it is called phase modulation. PM is a modulation pattern that we use for conditioning communication signals for transmission.

Frequency modulation works by continuously changing the strength of the transmitted signal about the information being sent.

FM radio uses frequency modulation. However, to understand frequency modulation, assume a signal with a low frequency and amplitude. As the signal passes, its frequency remains unchanged or unmodulated. We find that a signal carries very little information.

So, when you introduce information to this signal, there's a variation to the frequency that varies directly with the information. Also, when the frequency is modulated between low and high, the carrier frequency transmits music or voice. Therefore, we find that the frequency changes as a result, but the amplitude remains constant the entire time.

For example, the changes in the strength of the signal may be utilised to specify the sounds to be reproduced by the speaker, or the light intensity of television pixels.

How does an AM Work?

While receiving input signals, an AM receiver discovers amplitude variations in the radio waves at a specific frequency. It amplifies changes in the signal voltage to operate a loudspeaker or earphone.

Working Principle of an AM Receiver in Reality:

In this, a radio receiver is present in the opposite of a radio transmitter that uses an antenna to capture radio waves. Further, it processes those waves to elicit only those waves that are vibrating at the needed frequency and filters the audio signals that were added to those waves, following, amplifying the audio signal, and finally playing them on a speaker.

How does PM Work?

Phase modulation encodes a message or an input signal as variations in the instantaneous phase of a carrier wave.

In phase modulation, the working principle is that the instantaneous amplitude of the baseband signal modifies the phase of the carrier signal thereby keeping the constant amplitude and frequency. The phase of a carrier signal is modulated by phase modulation to follow the altering signal level or amplitude of the message signal.

Furthermore, the peak amplitude and the frequency of the carrier signal are also kept constant. However, as the amplitude of the message signal alters, the phase of the carrier also changes.

Difference Between AM and FM

Below is the table of AM versus FM:

Difference Between AM, FM, and PM

For a radio signal to carry audio or other information for broadcasting or two-way radio communication, signals must be modulated or changed in some way. Though we have several ways in which a radio signal may be modulated, one of the easiest is to change its amplitude in line with variations of the sound. Here, we discussed three types of modulation, viz: FM, AM, and PM, which will help you understand the basics of the modulation along with the difference between each.

Significance of The Difference Between AM FM and PM In Physics JEE Main 2025 

• JEE Main Physics section, questions related to modulation techniques—Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM)—are typically part of the Communication Systems chapter.

• Historically, this chapter contributes approximately 3.33% to the exam, equating to about one question per exam session. Therefore, while not heavily weighted, a clear understanding of these modulation methods is beneficial for securing marks in this area.

JEE Main 2025 Subject-Wise Important Chapters 

Important Study Materials Links for JEE Exams 2025

JEE Exams 2025, having the right study materials is crucial for success. The JEE Main and Advanced exams require a strong grasp of Physics, Chemistry, and Mathematics, as well as thorough practice with exam-style questions.

Access to quality resources, including sample papers, practice tests, and detailed notes, helps students review key topics and practice effectively.