A coil draws a current of 1.0 ampere and a power of 100 watt from an A.C. source of 110 volt and 5**√22/**π hertz. Find the inductance and resistance of the coil.

Why can't I use P=VI here, and how can I determine when to use P=VI or P=I^2 R or P=V^2 / R

### Asked by shaswattafs | 10th Jun, 2021, 06:21: PM

### Formulas for power , i.e., P = V × I , P = V^{2} / R and P = I^{2} R are used for DC circuits.

Above formulas are aslo used in AC circuits , if the AC circuits has only resistive loads like filament bulbs and heating coils.
In DC circuits or AC circuits with purely resistive loads , resistance of the circuit decides the current in the circuit and power dissipation.
When inductance and capacitance are present in AC circuit, then current and power dissipation depends on the impedence of the AC circuit .
Impedence of AC circuit is equivalenet of resistance of DC circuit, but impedence depends on frequency of alternating voltage source.
Impedence Z of AC circuit is given as ,
where R is resistance , X_{C} = 1/( C ω ) is capacitive reactance , C is capacitance and ω = ( 2πf ) is angular frequency if f is frequency of alternating voltage source and X_{L} = ( L ω ) is inductive reactance if L is inductance
Hence RMS Current in AC voltage source , I_{rms} = V_{rms} / Z
Power P = Z

^{2}/ R and P = I

^{2}R are used for DC circuits.

_{C}= 1/( C ω ) is capacitive reactance , C is capacitance and ω = ( 2πf ) is angular frequency if f is frequency of alternating voltage source and X

_{L}= ( L ω ) is inductive reactance if L is inductance

_{rms}= V

_{rms}/ Z

### Answered by Thiyagarajan K | 10th Jun, 2021, 07:13: PM

## Concept Videos

- what is the power of torch bulb rated at 2.5V and 500 mA?
- The MCB of a Rupa’s room is tripped and keeps on tripping again and again. If it is a domestic circuit, what could be the reason of this phenomenon?
- a current
- if 20 C of charge pass a point in a circuit in 1 second what current is flowing
- an electric bulb is related220 V and 100 W when it is operated on 110 V the power consumed will be
- Is on every consecutive point the electric potential or potential difference is different or same at all points except the ends of conductor
- what is potential difference?
- This is the question from class 10 light chapter asked in our state model paper
- In the following circuit the bulbis connected in parallel with switch and battery. the blub does not glow when the switch is closed but glows when the switch is open. Why?

### Kindly Sign up for a personalised experience

- Ask Study Doubts
- Sample Papers
- Past Year Papers
- Textbook Solutions

#### Sign Up

#### Verify mobile number

Enter the OTP sent to your number

Change