Question

A heater unit of negligible inductance has a resistance of 6.5Ω and is intended for use with 100V mains. For what 50Hz voltage would it be suitable when placed in series with an external apparatus, of negligible resistance, having an inductance of 0.01 H? If the frequency rises by 5 per cent and this voltage remains constant, what would be the resulting change of voltage at the heater terminals?