Electricity Flashcards
Describe direct current
Current is one direction only and may vary value
Give an example of a DC supply
Battery
Describe alternating current
Current repeatedly changes in direction and varies with value in time.
Give an example of an AC supply
Mains supply
The root mean square of ac voltage is the equivalent…
d.c. voltage that would produce the same power in a circuit as the a.c. voltage
The rms value is always less than…
the peak voltage of an a.c. supply
what is the rms formula
Vpeak = √2 Vrms
both measured in Volts (V)
√2 = 1.41…
That mains supply in the UK has an rms value of
230V
How can you find the frequency of an AC signal
The frequency of a signal can be found from the period (time for one complete wave) using T = 1/f
How can the period of an AC signal be found
The period can be found from the waveform on an osciliscope and looking at the time base setting.
Period (T) = number of divisions for one wave * time base
What is the peak voltage of the mains supply in the UK
325V
How can the peak voltage of an AC signal be found
Can be found from the amplitude of the waveform multiplied by the Y gain setting
How is rms current calculated
in the same way as RMS voltage
What is the rms current formula
I(peak) = √2 I(rms)
How is average power (power rating) calculated
using the rms values of current and voltage (P = I(rms)V(rms))
How is peak power calculated
using the peak values of current and voltage
Ppeak = IpVp
