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Ideal and practical sources, conversion

Short answer

Ideal voltage source: constant voltage, zero internal resistance; practical: series resistance, V = E−IRs. Ideal current source: constant current, infinite internal resistance; practical: parallel resistance, I = Is−V/Rp. Convert voltage to current: Is = E/Rs, Rp = Rs. Convert current to voltage: E = Is×Rp, Rs = Rp.

What do you mean by ideal and practical voltage and current source? Explain the method for converting practical voltage source into current source and vice versa.

Ideal and practical sources

  • Ideal voltage source: gives constant voltage E at any current; internal resistance zero.
  • Practical voltage source: an ideal source E in series with an internal resistance Rs; V = E − I Rs, so it falls as current rises.
  • Ideal current source: gives constant current Is at any voltage; internal resistance infinite.
  • Practical current source: an ideal source Is in parallel with a resistance Rp; I = Is − V/Rp.
 Practical V source        Practical I source
  o--[Rs]--o a              o--+------+--o a
    (E)                       (Is)   [Rp]
  o--------o b              o--+------+--o b

Converting voltage source to current source

Short-circuit current of the voltage source is E/Rs. So: Is = E/Rs, and Rp = Rs (connected in parallel).

Converting current source to voltage source

Open-circuit voltage of the current source is Is × Rp. So: E = Is × Rp, and Rs = Rp (connected in series).

Example

A 20 V source with Rs = 5 Ω is equivalent to a 4 A source with Rp = 5 Ω. A 2 A source with 10 Ω is equivalent to a 20 V source in series with 10 Ω.

The equivalence is valid only for the terminals seen from the load, not for the internal power loss.

✓ Answer checked by Claude Opus 5.5 (high effort)

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