FreeScienceLessonsMains electricity — fuses and safety in the home
Key facts
AC and DC — fill in the table
Type
Description
Oscilloscope trace
Direct current (DC)
Alternating current (AC)
Three-pin plug — fill in the table
Part
Details
Live wire
Neutral wire
Earth wire
Fuse
Circuit breaker
Transformers and the National Grid — fill in the table
Term
Detail
Transformer
Step-up transformer
Step-down transformer
Transformer equation
Power equation
High-voltage transmission
Exam questions — 4 questions · 12 marks
⚡ Extended questions included. Show all working for calculation questions. The AI marks against the real AQA mark scheme.
1 markEarth wire purposeAQA 8463 P1 style
Why does an electric kettle with a metal casing need an earth wire?
A The earth wire provides a return path for the current in normal operation
B If the live wire touches the casing, the earth wire provides a low-resistance path for a large current, blowing the fuse and making the appliance safe
C The earth wire prevents static electricity building up in the kettle
D The earth wire increases the efficiency of the appliance
4 marksTransformer calculationAQA 8463 P1 style
A step-up transformer has 500 turns on the primary coil and 10,000 turns on the secondary coil. The primary voltage is 25 V. (a) Calculate the secondary voltage. (b) If the primary current is 8 A, calculate the secondary current (assume 100% efficiency). (4 marks)
Hint: (a) Vp/Vs = np/ns — cross multiply to find Vs. (b) Vp × Ip = Vs × Is — rearrange for Is.
+40 XP
1 markWhy high voltage transmissionAQA 8463 P1 style
The National Grid transmits electricity at very high voltages (e.g. 400,000 V). Why?
A High voltage stores more energy that can be released when needed
B High voltage allows electricity to travel faster between power stations and homes
C High voltage reduces current, which reduces power lost as heat in cables (since P = I²R)
D High voltage is safer for workers to handle at the power station