Ever wondered how much energy your phone charger actually uses,...
Physics73 views·Updated 5 Jul 2026·2 pagesN5 Physics: Understanding Power, Current, and Voltage
1
of 2
Power Relationships
Your everyday electrical devices all have one thing in common - they convert electrical energy into other forms like light, heat, or sound. Power tells us how quickly this energy conversion happens, and it's directly linked to current and voltage.
The fundamental relationship is P = IV, where P is power (measured in watts), I is current (amperes), and V is voltage (volts). Think of it this way: more current or higher voltage means more power being used.
There's another useful form: P = I²R. This comes from substituting V = IR into our original equation. This relationship is particularly handy when you know the current and resistance but not the voltage directly.
Quick Check: A 3A current flowing through a 4Ω resistor uses P = 3² × 4 = 36W of power.
2
of 2
Power Calculations Made Simple
The third power equation, P = V²/R, is brilliant for situations where you know voltage and resistance. It comes from rearranging Ohm's law and substituting into P = IV.
These three equations give you flexibility in calculations - you can find power using any two of the three electrical quantities (voltage, current, resistance). Choose whichever equation fits the information you're given.
Here's your complete toolkit: P = E/t (energy per time), P = IV (voltage-current), P = I²R (current-resistance), and P = V²/R (voltage-resistance). Master these, and you'll breeze through any power calculation.
Exam Tip: Always check your units! Power should come out in watts (W), and remember that 1000W = 1kW.
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Physics73 views·Updated 5 Jul 2026·2 pagesN5 Physics: Understanding Power, Current, and Voltage
Ever wondered how much energy your phone charger actually uses, or why some devices get hot when they're working? Power relationshipsin electricity help us understand how electrical energy flows and gets converted in circuits - knowledge that's essential for...
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Power Relationships
Your everyday electrical devices all have one thing in common - they convert electrical energy into other forms like light, heat, or sound. Power tells us how quickly this energy conversion happens, and it's directly linked to current and voltage.
The fundamental relationship is P = IV, where P is power (measured in watts), I is current (amperes), and V is voltage (volts). Think of it this way: more current or higher voltage means more power being used.
There's another useful form: P = I²R. This comes from substituting V = IR into our original equation. This relationship is particularly handy when you know the current and resistance but not the voltage directly.
Quick Check: A 3A current flowing through a 4Ω resistor uses P = 3² × 4 = 36W of power.
2
of 2Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Power Calculations Made Simple
The third power equation, P = V²/R, is brilliant for situations where you know voltage and resistance. It comes from rearranging Ohm's law and substituting into P = IV.
These three equations give you flexibility in calculations - you can find power using any two of the three electrical quantities (voltage, current, resistance). Choose whichever equation fits the information you're given.
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Exam Tip: Always check your units! Power should come out in watts (W), and remember that 1000W = 1kW.
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Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
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