P5.1 Alternating curretns Flashcards
What is direct current?
Where current goes around the circuit in one direction
Is mains electricity alternating or direct?
Alternating supply
What is an alternating current?
Repeatedly reverse its direction - it flows one way then the opposite way in successive cycles
What is mains frequency in the UK?
50 cycles per second
Why is the live wire dangerous?
Because it repeatedly changes direction from + to - and back every cycle
What is the national grid?
A nationwide network of cables and transforemers
What are step-up transformers?
Makes the potential difference larger
What are Step-down transformers?
Used to supply electricity from the National grid to consumers - decreases the p.d
Why is the national grid an efficient way to transport power?
As potential difference is increased - much less current is needed to transfer the same amount of power - so power loss due to the resistance heating in the cables is much reduced
What does an oscilloscope show?
How an alternating potential difference changes with time
What is the Y-gain?
Controls how tall the waves are
What is the time base?
Changes how many waves fit across the screen
What is the equation for frequency?
1/time taken for 1 cycle
