The potential difference at the terminals of an open current source is 5 V. Determine the internal resistance

The potential difference at the terminals of an open current source is 5 V. Determine the internal resistance of the current source if, with a resistance of the outer section of the circuit of 5 Ohm, the current is 0.8 A

These tasks: φ1 – φ2 (potential difference at the terminals of the open source) = 5 V; R (the resistance that the outer section of the circuit has) = 5 ohms; I (effective current) = 0.8 A.

The internal resistance of the current source under consideration can be calculated from the formula: φ1 – φ2 = I * (R + r) and r = φ1 – φ2 / I – R.

Let’s make the calculation: r = 5 / 0.8 – 5 = 6.25 – 5 = 1.25 Ohm.

Answer: The current source in question has an internal resistance of 1.25 ohms.