Home » CBSE Class 12th Physics Notes for Chapter 7 Alternating Current

CBSE Class 12th Physics Notes for Chapter 7 Alternating Current

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  CHAPTER 7 ALTERNATING CURRENT

 

  • An alternating voltage v = vm sin ωt applied to a resistor R drives a current i = im sinωt in the resistor, im=vm/R . The current is in phase with the applied voltage.

 

  • For an alternating current i = im sin ωt passing through a resistor R, the average power loss P due to joule heating is (1/2) i2m

 

  • The phase relationship between current and voltage in an ac circuit can be shown by representing voltage and current by rotating vectors called phasors.

 

  • A phasor is a vector which rotates about the origin with angular speed ω.

 

  • The magnitude of a phasor represents the amplitude or peak value of the quantity (voltage or current) represented by the phasor.

 

  • Transformer: A transformer consists of an iron core on which are bound a primary coil of Np turns and a secondary coil of Ns

 

  • If the secondary coil has greater turns that the primary, the voltage is stepped up and the transformer is called a step-up transformer.

 

  • If the secondary coil has less number of turns than the primary coil, the voltage is stepped down and the transformer is called a step-down transformer.

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