Alternating currents

Question 1

What is alternating current or voltage?

Answer 1

• one that changes direction at time
• voltage acrtoss a resistance goes up and down in a regular pattern
  
  • some of the time its positive and some of the time its negative

Question 2

What is an oscilliscope used for>?

Answer 2

• display the voltage of an alternating current (and direct too)
• like fancy voltmeters
• vertical heigh of the trace at any point shows the input voltage at that point

Question 3

What is the grid on the oscilliscope?

Answer 3

• select how many volts per division you want on the y axis scale to represent the y-gain control dial

Question 4

What is the pattern of an alternating current and a DC?

What happens if you turn time base off?>

Answer 4

• gives a regularly repeating sinusodial waveform
• DC gives straigh line, always same voltage
• time base off - displayed as vertical line for ac, and dot for DC

Question 5

What is peak voltage?

Answer 5

• `V₀
• ampltude

Question 6

What is peak-to-peak voltage?

Answer 6

• distance between peak to trough

Question 7

Peak voltage of ac = 2.0V

whyu will this not have a same power supply a 2V dc

what do you need to do to compare?

Answer 7

• will be below 2 V most of the time
• won’t have as high power output as 2 V dc supply
• need to take root mean squre (rms) voltage
  
  • equation on data sheet
  • same can be done for current

Question 8

How do you work of the rms power?

Answer 8

• power_rms = I_rms x V_rms

Question 9

How is the freq on a oscilliscoep worked out

Answer 9

• as long as time base setting is known
• 1 / T
• measuer distance between successive peaks along the time (horizontal) axis gives time period

Question 10

What is the UK’s mains electrical supply?

Answer 10

• 230 V although it does vary
• it is the rms value