A wire l1 = 10 m long has a resistance R1 = 150 Ohm. How long should the wire have for its resistance to be R2 = 60Om?

Wire resistance can be represented by the formula:

R = ρ * l / S.

Since the electrical resistance of the wire and its cross-section are constant, the ratio will be true:

R1 / l1 = ρ / S = R2 / l2, where according to the condition R1 (initial wire resistance) = 150 Ohm, R2 (final wire resistance) = 60 Ohm, l1 (initial wire length) = 10 m.

Let’s do the calculation:

l2 = R2 * l1 / R1 = 60 * 10/150 = 4 m.

Answer: The wire should be 4 meters long.