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Physics Tutor in Pal Gam Surat – Learn AC Power Factor, NEET Physics, IIT-JEE Physics and Board Physics with Kumar Sir

+91-9958461445

Pal Gam Surat is one of the fast-growing residential areas of Surat. Families living in Pal Gam, Pal Road, Adajan, Palanpur, Bhatha and nearby localities give strong importance to education, career and professional success. Pal Gam is known as a developing locality with good residential options, connectivity, schools, hospitals and shopping facilities.

If you live in Pal Gam Surat and Physics is not becoming clear, then the problem is not always hard work. Sometimes the real problem is the teaching method. Many students read NCERT, attend coaching, solve modules, but still get confused in concepts like AC circuits, power factor, current, voltage, resistance, capacitor, inductor, phase difference and average power.

This is where Kumar Sir can help.

For NEET, IIT-JEE, CBSE, Gujarat Board, IB, IGCSE and A-Level Physics, Kumar Sir teaches Physics from the root level. He explains every formula, every graph, every derivation and every numerical in a simple and logical way.

Contact Kumar Physics Classes: +91-9958461445
Website: Kumar Physics Classes

What is Power Factor in AC Circuit?

In an AC circuit, voltage and current may not always be in the same phase. In a pure resistor, current and voltage are in the same phase. But in an inductor or capacitor, current and voltage have a phase difference.

Power factor is defined as:

Power Factor = cos φ

Here, φ is the phase difference between voltage and current.

If voltage and current are in the same phase, φ = 0°, so cos φ = 1. This is the best condition because maximum power is used.

If voltage and current have a large phase difference, power factor becomes low. That means the circuit is drawing current, but useful power is less.

Significance of Power Factor

Power factor tells us how effectively electrical power is being used in an AC circuit.

Average power in AC circuit is:

Pavg = Vrms Irms cos φ

Here, cos φ is the power factor.

So, power factor directly controls average power. If power factor is high, useful power is high. If power factor is low, useful power is low.

For students preparing for NEET and JEE, power factor is very important because it connects AC circuit theory with real electrical power usage.

Why Students in Pal Gam Surat Need Strong Physics Guidance

A student may live in a good locality, attend a good school, and still struggle in Physics. The reason is simple: Physics needs conceptual clarity. Memorising formulas is not enough.

If you do not understand phase difference, impedance, reactance, resonance and power factor, AC circuit numericals become confusing.

Kumar Sir teaches these topics step by step:

Meaning of AC voltage and AC current
RMS value and peak value
Resistance, inductive reactance and capacitive reactance
Impedance triangle
Phase angle
Power factor
Average power
Resonance condition
NEET and JEE numerical practice

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Why Kumar Sir?

Kumar Sir focuses on concept building first. He does not simply give formulas. He explains why the formula is used, where it comes from and how to apply it in NEET, JEE and board exams.

For AC power factor, he explains:

Why current lags in an inductor
Why current leads in a capacitor
Why resistor has power factor 1
Why pure inductor and pure capacitor consume zero average power
Why real circuits need good power factor
How power factor affects average power

This type of teaching makes Physics logical and interesting.

Final Message for Students of Pal Gam Surat

If you are living in Pal Gam Surat and Physics is creating pressure in NEET, IIT-JEE, CBSE or Gujarat Board, do not wait. Physics can become your strongest subject if it is taught properly.

Call Kumar Sir and start learning Physics with clarity, confidence and proper exam direction.

Kumar Physics Classes
Contact: +91-9958461445
Website: https://kumarphysicsclasses.com

Power Factor AC Circuits | Kumar Physics Classes

Power Factor in AC Circuits

RL Circuit | RC Circuit | RLC Circuit | Resonance | Impedance

What is Power Factor?

Power factor is the cosine of the phase angle between AC voltage and AC current. It tells how effectively electrical power is converted into useful average power.

Power Factor = cos φ = R / Z

Average Power in AC Circuit

In AC circuits, voltage and current may not be in the same phase. Therefore, average power depends on power factor.

Pavg = Vrms Irms cos φ

Power Factor in Different Circuits

Pure Resistor: φ = 0°, Power Factor = 1
Pure Inductor: φ = 90°, Power Factor = 0
Pure Capacitor: φ = 90°, Power Factor = 0
RL Circuit: Current lags voltage, PF = R / √(R² + XL²)
RC Circuit: Current leads voltage, PF = R / √(R² + XC²)
RLC Circuit: PF = R / √[R² + (XL − XC)²]
Resonance: XL = XC, Z = R, PF = 1

40 Conceptual Questions with Answers

Q1. What is power factor?

Power factor is cos φ, where φ is the phase difference between voltage and current.

Q2. What is the power factor of a pure resistor?

It is 1 because voltage and current are in the same phase.

Q3. What is the power factor of a pure inductor?

It is zero because current lags voltage by 90°.

Q4. What is the power factor of a pure capacitor?

It is zero because current leads voltage by 90°.

Q5. Why is average power zero in pure L and pure C circuits?

Because cos 90° = 0, so Pavg = Vrms Irms cos φ = 0.

Q6. What is impedance?

Impedance is the total opposition offered by an AC circuit to current.

Q7. What is impedance of RL circuit?

Z = √(R² + XL²)

Q8. What is impedance of RC circuit?

Z = √(R² + XC²)

Q9. What is impedance of series RLC circuit?

Z = √[R² + (XL − XC)²]

Q10. When does resonance occur in RLC circuit?

Resonance occurs when XL = XC.

Q11. What is power factor at resonance?

Power factor is 1.

Q12. Why is current maximum at resonance?

Because impedance becomes minimum and equal to R.

Q13. In RL circuit, does current lead or lag?

Current lags behind voltage.

Q14. In RC circuit, does current lead or lag?

Current leads the voltage.

Q15. What is inductive reactance?

XL = ωL. It is opposition due to inductor.

Q16. What is capacitive reactance?

XC = 1/ωC. It is opposition due to capacitor.

Q17. What happens to XL when frequency increases?

XL increases because XL = 2πfL.

Q18. What happens to XC when frequency increases?

XC decreases because XC = 1/2πfC.

Q19. Why is power factor important?

It tells how much supplied power is actually converted into useful power.

Q20. What is the ideal power factor?

The ideal power factor is 1.

Q21. What is poor power factor?

A low value of cos φ means poor power factor.

Q22. Why do industries improve power factor?

To reduce current loss and improve efficiency.

Q23. Which device improves lagging power factor?

A capacitor is commonly used.

Q24. In RL circuit, power factor is lagging or leading?

It is lagging.

Q25. In RC circuit, power factor is lagging or leading?

It is leading.

Q26. What is wattless current?

Current component that does not contribute to average power is called wattless current.

Q27. Why is pure inductor called wattless?

Because average power consumed is zero.

Q28. Why is pure capacitor called wattless?

Because it stores and returns energy without net consumption.

Q29. What is active power?

Active power is useful power: P = VI cos φ.

Q30. What is apparent power?

Apparent power is VI.

Q31. What is reactive power?

Reactive power is VI sin φ.

Q32. In resonance, what is phase angle?

Phase angle is zero.

Q33. At resonance, what is impedance?

Impedance is minimum and equal to R.

Q34. At resonance, what is current?

Current is maximum.

Q35. What is resonant frequency?

f = 1 / 2π√LC

Q36. If XL > XC, circuit behaves like what?

It behaves like an inductive circuit.

Q37. If XC > XL, circuit behaves like what?

It behaves like a capacitive circuit.

Q38. If XL = XC, circuit behaves like what?

It behaves like a pure resistive circuit.

Q39. Why is power factor maximum at resonance?

Because phase difference becomes zero and cos φ = 1.

Q40. What is the relation between power factor and impedance?

Power factor = R/Z.