Physics

Electrical Machines and Circuits

754 Questions

Electrical machines and circuits involve the principles of alternating and direct current, transformers, diodes, and power consumption. These concepts are essential for engineering and technical exams. Review these practice questions to test your knowledge of circuit analysis.

Transformers and impedanceAlternating and direct currentCircuit components and diodesPower consumption calculations

Electrical Machines and Circuits Questions

Multiple choice

Assume that the switch S is in position 1 for a long time and thrown to position 2 at t = 0.

At t = 0+, the current i1 is
  1. $\dfrac{-V}{2R}$
  2. $\dfrac{-V}{R}$
  3. $\dfrac{-V}{4R}$

  4. zero
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When the switch is in position 1 for a long time, the inductor reaches steady state with current I = V/R flowing through it (inductor acts as short circuit in DC steady state). At t=0+, the inductor current cannot change instantaneously, so it remains V/R. In position 2, this current flows through 2R, creating a voltage of -V/2R across the inductor to oppose the change.