For DC arc welding, voltage V (V) and arc length l (cm) satisfy V = 30 + 30l. Open-circuit voltage is 80 V. Find maximum possible arc length (two decimals cm).
The limiting arc voltage cannot exceed the source’s 80 V open-circuit voltage. Setting $30+30l=80$ gives $l=50/30=1.6667$ cm, or **1.67 cm**. This is a limiting upper bound; a sustained nonzero-current arc requires the loaded source characteristic.
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