How It Works: Why High-Current Appliances Cost More
Part of Electrical Power & Energy — GCSE Physics
This how it works covers How It Works: Why High-Current Appliances Cost More within Electrical Power & Energy for GCSE Physics. Revise Electrical Power & Energy in Electricity for GCSE Physics with 15 exam-style questions and 30 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 6 of 15 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 6 of 15
Practice
15 questions
Recall
30 flashcards
⚙️ How It Works: Why High-Current Appliances Cost More
Power in an electrical circuit represents the rate of energy transfer — how many joules of electrical energy are converted into other forms (heat, light, sound, kinetic) every second.
The equation P = I²R reveals something important: power increases with the square of the current. Doubling the current quadruples the power dissipated as heat in a resistor. This is why:
- High-current appliances (showers, kettles) are very expensive to run
- National Grid transmits electricity at very high voltage and low current to minimise energy losses in cables (P = I²R — lower I = far less heating loss)
- Fuses are rated by current — too much current means dangerous overheating
The equation P = V²/R shows that at a fixed voltage (like mains 230 V), lower resistance means more power. This is why a kettle (low resistance heating element) is much more powerful than an LED bulb (high resistance).
Quick Check: A toaster operates at 230 V with a current of 4 A. Calculate its power rating.
P = I × V = 4 × 230 = 920 W.