Knock out the false AC claims

Exercise and reference answers

Questions

1. Question

   Three of these statements about a series RLC circuit at resonance are false.

   Choices

   1. Item

      Impedance drops to just the resistance

      Correct

      Yes

   2. Explanation

      Series resonance gives the smallest impedance.

      Item

      Impedance climbs to its highest value

   3. Explanation

      Current peaks because the impedance is least.

      Item

      The loop current falls away to zero

   4. Explanation

      The reactances cancel, so the power factor is one.

      Item

      The power factor sits at zero there

2. Question

   Three of these statements about the Indian mains supply are false.

   Choices

   1. Explanation

      Peak is RMS times root two, about 325 V.

      Item

      Its RMS and peak are both 230 V

   2. Explanation

      Sixty hertz is the United States figure.

      Item

      It runs at sixty hertz

   3. Item

      Its RMS is 230 V and peak near 325 V

      Correct

      Yes

   4. Explanation

      A full cycle of a pure sine averages to zero.

      Item

      A full sine cycle averages 230 V

Instructions

Tap the three false lines in each set about series resonance and mains supply.

Explanation