AC source (12 V~ 50 Hz adapter / signal generator) · Exterior view
  1. 1Voltage indicator (V~, effective value)
  2. 2Frequency indicator (Hz)
  3. 3Voltage setting
  4. 4Frequency setting (50 / 60 Hz)
  5. 5On / off switch
  6. 6Output terminals (~ red, ~ black) · green: chassis ground
Enclosed adapter marked 12 V~ or a generator with BNC output
Enclosed adapter box or benchtop generator; size depends on the model
Power supply

AC source (12 V~ 50 Hz adapter / signal generator)

In simple terms
What is this?

Electricity that keeps changing direction. It goes back and forth like a pump pushing water to and fro.

What is it for?

It is the starting point for rectifier and filter experiments; unlike a battery, it does not flow in one direction only.

Where do you see it?

The electricity in a wall socket comes and goes like this too; on the bench we use a safe, low-voltage version of it.

How do you spot it?

A closed adapter box or a desktop device with knobs; it has two output terminals and no plus or minus.

Caution:

Never connect it to a wall socket yourself; use only an insulated, low-voltage adapter.

Technical definition

A source whose voltage changes direction over time. An isolated 12 V~ adapter supplies a 50 Hz sine; a signal generator is a source with adjustable waveform and frequency, usually with less current. The Lab uses low voltage only; a mains outlet is not an experiment source.

Voltage12 V RMS
Frequency50 Hz
WaveSine
Schematic symbol Same in IEC and ANSI

IEC 60617: the drawing style used in Türkiye and Europe.

Pins 2
1Reference direction pFirst AC terminal or the generator’s signal output; not a fixed plusp
2Return nSecond AC terminal; the generator’s BNC shield may be groundedn
Features typical
Voltage
12 V RMS (adapter example)
Frequency
50 Hz (adapter example)
Wave
Sine; adjustable on the generator
Peak voltage
≈17 V (12 V RMS sine)
Peak-to-peak
≈34 V (12 V RMS sine)
Output current
By the adapter’s VA rating / the generator’s limit
Generator load
Typically 50 Ω output; the load setting affects the amplitude
Safety
Isolated low-voltage output; no mains in the Lab
Example part
Isolated 12 V~ 50 Hz adapter; a signal generator as an alternative
Common mistakes
Confusing RMS with peakThe peak value of a 12 V~ sine is about 17 V. Check the parts’ voltage limits against the peak.
Measuring with the DC rangeAC with a zero average can read about zero in DC mode. Use V~ for voltage.
Thinking every output is isolatedThe generator’s BNC shell may be tied to protective ground. Verify isolation from the manufacturer’s documentation; do not connect to mains.

Test with a multimeter

Test whether this part is good with the multimeter on the measurement screen.

Take a measurement
Where it is used
Bridge rectifier experimentMeasuring AC voltage and RMSEffect of frequency on a filter
Related lessons
Rectifying with a diode
Module 4 · Diode and transistorsoonMeasuring voltage
Module 2 · Measuring with a multimetersoonFiltering the power supply
Module 3 · Capacitor and timesoon
Try it in the Lab