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NEETPhysicsElectromagnetic Induction

Consider the following four mathematical expressions for current i as a function of time t : (I) i = I₀ ( t) (II) i = I₀ + I₀ ( t) (III) i = I₀ ( t) (IV) i = I₀ ^2( t) Which of these expressions represent an alternating current (AC)?

Options

  1. AOnly (I) and (III)
  2. B(I), (II), (III) and (IV)
  3. COnly (I), (II) and (III)
  4. DOnly (I)

Correct answer

A. Only (I) and (III)

Step-by-step solution

An alternating current (AC) is one that periodically reverses its direction, meaning its mathematical expression must take both positive and negative values. (I) i = I₀ ( t) varies between +I₀ and -I₀ . It reverses polarity, so it is AC. (II) i = I₀ + I₀ ( t) varies between 0 and 2I₀ . It never becomes negative, so it is a pulsating direct current (DC). (III) i = I₀ ( t) varies between +I₀ and -I₀ . It reverses polarity, so it is AC. (IV) i = I₀ ^2( t) varies between 0 and I₀ (since the square of a real number is n

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