If there is no current flowing through a resistor, Ohm's Law tells us that the voltage across the resistor will be zero. Ohm's Law states that voltage (V) is equal to the product of current (I) and resistance (R), represented by the formula:
V = I * R
Since the current (I) is zero, any value multiplied by zero will result in zero voltage across the resistor. In summary, when no current flows through a resistor, the voltage across it is zero. This is true for any ideal resistor in an ideal circuit.