Flashcards in Mains Electricity Deck (15):
What is electric current?
The movement of charge carriers
What is the voltage of the mains?
What kind of supply is the mains? What does this mean?
AC (alternating current). It is constantly changing direction
What is the frequency of mains supply?
50 cycles per second or 50 Hz
What kind of supply is a battery? What does this mean?
DC (direct current) - the current keeps flowing in the same direction
What can electrical supplies be shown on?
An oscilloscope screen
What is a CRO?
A cathode ray oscilloscope is basically a voltmeter
What happens when you plug an AC supply into an oscilloscope?
You get a 'trace' on the screen that shows how the voltage of the supply changes with time. The trace goes up and down in a regular pattern - sometimes +ve, sometimes -ve
What happens when you plug an DC supply into an oscilloscope?
The trace you get is a straight line
What does the vertical height of an AC trace show?
The input voltage at that point. By measuring the height of the race you can find the p.d of the AC supply
What represents the voltage on a DC oscilloscope trace?
The distance from the straight line trace to the centre line (vertical)
What does the gain dial control on an oscilloscope?
How many volts each centimetre division represents on the vertical axis
What does the timebase dial control on an oscilloscope?
Controls how many milliseconds each division represents on the horizontal axis
What is the equation for frequency?
Frequency (Hz) = 1/Time period (s)