A current-carrying rectangular loop PQRS is made of uniform wire. The length PR = QS = \( 5 \, \text{cm} \) and PQ = RS = \( 100 \, \text{cm} \). If the ammeter current reading changes from \( I \) to \( 2I \), the ratio of magnetic forces per unit length on the wire PQ due to wire RS in the two cases respectively \( F^{I}_{PQ} : F^{2I}_{PQ} \) is:
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The magnetic force between parallel wires varies with the product of the currents. If a current doubles, the force increases by the square of the change factor.