AC Generator and Transformer
Working principle, turns ratio and sources of energy loss. (Physics › Electromagnetic Induction and Alternating Currents, NEET UG syllabus.)
What is AC Generator and Transformer?
A device that converts mechanical energy into alternating electrical energy based on the principle of electromagnetic induction.
Key formula / rule: Induced EMF in AC Generator
Key points
- Describe the working principle and construction of an AC generator.
- Derive the expression for induced EMF in an AC generator.
- Explain the working principle and construction of a transformer.
- Apply the turns ratio formula for ideal transformers to solve problems.
Common exam trap
Confusing the energy conversion in AC generator (mechanical to electrical) with electric motor (electrical to mechanical).
Definitions
- Term
AC Generator
- Meaning
A device that converts mechanical energy into alternating electrical energy based on the principle of electromagnetic induction.
- Term
Transformer
- Meaning
A static electrical device that transfers electrical energy between two or more circuits through electromagnetic induction, primarily used to change AC voltage levels.
- Term
Mutual Induction
- Meaning
The phenomenon where a changing current in one coil induces an electromotive force (EMF) in a nearby coil.
- Term
Eddy Currents
- Meaning
Circulating currents induced in the bulk of a conductor when subjected to a changing magnetic flux, leading to energy loss in the form of heat.
- Term
Laminated Core
- Meaning
A core made of thin, insulated sheets of soft iron, used in transformers to increase resistance to eddy currents and thus reduce energy loss.
Learning objectives
Describe the working principle and construction of an AC generator.
Derive the expression for induced EMF in an AC generator.
Explain the working principle and construction of a transformer.
Apply the turns ratio formula for ideal transformers to solve problems.
Identify and explain different types of energy losses in a real transformer.
Understand the role of a laminated core in reducing eddy current losses.
Formulae
- Name
Induced EMF in AC Generator
- Note
N = number of turns, B = magnetic field strength, A = area of coil, ω = angular frequency, t = time. E₀ = NBAω is the peak EMF.
- Expression
E = NBAω sin(ωt)
- Name
Transformer Turns Ratio (Ideal)
- Note
Vs, Vp = secondary/primary voltage; Ns, Np = secondary/primary turns; Is, Ip = secondary/primary current. Note the inverse relationship for current.
- Expression
Vs / Vp = Ns / Np = Ip / Is
- Name
Transformer Efficiency
- Note
Pout = output power, Pin = input power. For an ideal transformer, η = 100%.
- Expression
η = (Pout / Pin) * 100% = (Vs Is / Vp Ip) * 100%
Prerequisites
Faraday's Law of Electromagnetic Induction
Lenz's Law
Magnetic Flux
Mutual Induction
Basic understanding of AC circuits
Common mistakes
Confusing the energy conversion in AC generator (mechanical to electrical) with electric motor (electrical to mechanical).
Applying transformer formulas for DC circuits.
Incorrectly relating current and voltage in the turns ratio (Ip/Is, not Is/Ip for Vs/Vp).
Forgetting the purpose of a laminated core (reducing eddy currents).
Assuming ideal transformer conditions (100% efficiency) for all problems without checking.
Keywords
AC Generator
Alternator
Faraday's Law
Electromagnetic Induction
Transformer
Mutual Induction
Step-up Transformer
Step-down Transformer
Turns Ratio
Energy Loss
Copper Loss
Eddy Currents
Hysteresis Loss
Laminated Core
Efficiency
Practice preview
A transformer operates on the principle of:…
easy
A step-down transformer has 1000 turns in its primary coil and 100 turns in its secondary coil. If the input voltage is 220 V, what is the output voltage?…
medium
The peak value of the induced EMF in an AC generator with N turns, rotating with angular velocity omega in a uniform magnetic field B, and having an armature area A, is given by:…
hard