how to check current is AC or DC

To check if a current is AC or DC, you can use a multimeter to measure the voltage, and observe the waveforms on an oscilloscope or directly by looking at the multimeter reading. AC is characterized by a fluctuating, wavy line on the display and a constant value, DC is a constant value. 

Here’s a breakdown of how to differentiate between AC and DC:

1. Using a Multimeter:

• AC Voltage Measurement:
  • Set your multimeter to AC voltage (marked with a “V” and a wavy line “~”).
  • Measure the voltage.
  • If the multimeter displays a fluctuating value, the current is AC.
• DC Voltage Measurement:
  • Set your multimeter to DC voltage (marked with a “V” and a solid and dashed line “⎓”).
  • Measure the voltage.
  • If the multimeter displays a steady, constant value, the current is DC. 

2. Visual Inspection of the Waveform

• AC Waveform: The voltage in AC current fluctuates periodically, resulting in a sinusoidal or a similar waveform, where the current changes direction back and forth.
• DC Waveform: DC Current flows in only one direction and the waveform is a constant line 

3. Other Considerations

• Circuit Symbols:AC and DC sources have different circuit symbols. AC sources typically have a wavy line, while DC sources have a straight line or “+” and “-” symbols representing the fixed polarity. 
• Polarity:DC current flows in one direction, which means one terminal is marked as positive (+) and the other as negative (-). 
• Marking on the device:Some devices have markings on them such as “12V DC” to indicate that the device needs a certain DC voltage supply or “240V AC” indicating the AC voltage that the appliance needs.