An electronic appliance consists of a series RCL circuit, designed to operate at

Question

An electronic appliance consists of a series RCL circuit, designed to operate at resonance when
plugged into a 120-V (rms), 60-Hz source, which is the standard for wall outlets in the US. When
operated at this voltage and frequency, the power output is 4.0 kW (kilowatts). The appliance's
capacitance is C = 153 ?F.
Suppose you take this device to Europe, where wall outlets supply 220-V, 50-Hz electrical service. If
you connect it to a wall outlet without using an adaptor plug, will it run at a higher or lower power?

Explanation / Answer

sol Electrical equipment is made by the manufacturer only for a certain frequency and cannot be used on an other frequency! In some cases it is made to be used for both frequencies and in that case specifically mentioned on the type plate: 50/60 Hertz. Example: Battery charger for a laptop computer. On the typeplate is mentioned: 100-240 Volt and 50/60 Hertz (which means any voltage between 100 and 240 volt plus can be used on either 50 or 60 Hertz) Why you cannot use it on the other frequency: - because the internal current goes up and this might cause faster deteriation of the insulation on the wiring, which causes shortcircuit and this may lead to fire, which can burn down your house! What happens: In transformers (like input transformer of the equipment) the current goes up. In motors (like cooling ventilator or compressor) also the current goes up, the turns of the motor depends on the frequency, which means the turns are 17% higher if you go from 50 Hertz to 60 Hertz and 17% lower if you go from 60 Hertz to 50 Hertz, plus in this case the internal cooling is lower! Can I do anything in order to still use the equipment on an other frequency? Yes you can but at your own risk, you still cannot change the effect of higher or lower turns, but you can lower the current: Lower the voltage to the equipment with about 20% as mentioned on the typeplate, buy means of a transformer.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.