The Expensive Shower
⚡ The Expensive Shower
P = IV — Use when you know current AND voltage
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🧠 Memory Aid
Three power equations from one — "PIV is like PIE":
Start with P = IV (the PIE). To get P = I²R: replace V with IR (from Ohm's Law). To get P = V²/R: replace I with V/R. You only need to remember P = IV and V = IR, then derive the others.
kWh billing — "kW × Hours = kWh":
Kilowatts × Hours = Kilowatt-Hours. The unit tells you exactly what to multiply. If given watts, divide by 1000 first. If given time in minutes, divide by 60 first.
Which equation? — "Got V and I? Use P = VI. Got I and R? Use I²R. Got V and R? Use V²/R":
Match the letters in the equation to the letters of the quantities you've been given in the question.
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Quiz · Question 1 of 15
What is the unit of electrical power?
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This topic in real past papers
Every real exam question we've found on electrical power & energy, with a full worked answer.