Class 12 Physics Alternating Current Alternating Current

Alternating Current

  • Alternating current is defined as the current that varies  like a sine function with time.
  • The value  of current will oscillate  between a maximum value and a minimum value.
  • In case  of  AC  the current is  changing  its  magnitude at every instant of time.
  • The direction of current will be clockwise  and  anticlockwise and it will keep on repeating.
  • Frequency of  the alternating  current is  defined  as  how fast  the electrons are changing  their directions. For example: If frequency is  20Hz  this means electrons are moving back  and forth 20 times in a second.
  • DC  voltage  gives  rise  to  DC  current  similarly  AC  voltage  give  rise  to  AC  current.
  • Alternating current is expressed as: - I = Im sinωt  
    • Where Im = maximum or peak value  of  the AC .
  • Alternating voltage is expressed as: - V = Vm sinωt  
    • Where Vm = peak value of the voltage.

Causes of  alternating current

  • When a rotating magnet is considered instead of steady magnetic field then both the poles of the magnet will keep on changing as a result the direction of electrons also gets reversed.

This results oscillation of electrons which give rise to current and this current is known as alternating current.

 

(AC as a sine wave function)

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