A parallel circuit has value of RT = R1 // R2 // R3. If one resistor opens, RT

RT increases?

If RT ia the total R then Rt increases

thank you

In a parallel circuit, the total resistance (RT) is given by the reciprocal of the sum of the reciprocals of the individual resistances (R1, R2, R3).

In this case, RT = 1/(1/R1 + 1/R2 + 1/R3).

If one resistor opens, it means that the circuit is broken at that point and current can no longer flow through that particular resistor.

When a resistor opens in a parallel circuit, the total resistance across the circuit increases. This is because the reciprocal of a larger resistance value is smaller, hence adding an infinite resistance (due to the open resistor) will increase the total resistance.

Therefore, when a resistor opens, RT increases.