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Power of a Device
Electrical power is the rate at which a device transfers or converts electrical energy.
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Power of a Device
Recommended for Class 10
Power of a Device
Electrical power is the rate at which a device transfers or converts electrical energy.
**P = Wt**
In an electric circuit:
**P = VI**
Using Ohm's law, for a resistor:
**P = I²R**
and:
**P = V²R**
Unit:
watt (W)
Meaning of Power Rating
A 60 W lamp transfers approximately 60 J of energy each second when operating at its rated conditions.
Worked Example
A device operates at:
`V = 12 V`
`I = 2 A`
**P = VI**
`P = 12×2`
**P = 24 W**
Power of a Device — Advanced
Common Mistakes
Common Mistakes
- Mistake
Power is not energy.
- Mistake
Power tells how quickly energy is transferred.
- Mistake
Use formulas that match the known quantities.
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- Definition
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Practice
PQ
Q1. Define electrical power.
PQ
Q2. State `P=VI`.
PQ
Q3. Calculate 230 V × 2 A.
PQ
Q4. Explain 50 W rating.
PQ
Q5. Calculate P for I=3 A, R=4 Ω.
Exam Practice
EQ
Q1. Define power.
EQ
Q2. Derive/use alternative formulas.
EQ
Q3. State watt meaning.
EQ
Q4. Numerical.
EQ
Q5. Explain appliance rating.
School-standard facts for Matric and Intermediate. Original explanations — not copied from textbooks.