electricity - types of current

Question 1

direct current

Answer 1

the current flows around in one direction, from negative to positive
flows in circuits powered by batteries and solar cells

Question 2

alternating current

Answer 2

the current flows both ways, charging direction regularly
flows in mains electricity circuits, and from generators
our mains electricity has a frequency of 50Hz and a peak voltage of 230V

Question 3

what is an oscilloscope

Answer 3

a piece of apparatus that can be used to measure the voltage and frequency of an alternating current

a DC supply will show a horizontal trace because current flows in one direction

an AC supply will show a wave because voltage is constantly changing direction

Question 4

the y-sensitivity setting

Answer 4

to calculate the voltage: multiply amplitude by y-sensitivity setting

increasing the y-sensitivity dial - increase the range of the oscilloscope - decrease precision

Question 5

peak voltage and time base dial

Answer 5

size of the voltage is always changing -> measure the peak voltage (amplitude x y-sensitivity setting)

time base dial: adjust the wavelength of the displayed wave - increasing the setting will squash the wave to fit more cycles on the screen

Question 6

measuring frequency

Answer 6

you cannot measure frequency but you can measure the time period and use it to calculate frequency

time period is calculated by multiplying the wavelength of the wave (distance between corresponding points) by the time-base setting
–> this tells you how long 1 cycle will take in milliseconds

frequency = 1/time period