Question

Fluorescent lights often use an inductor, called a ballast, to limit the current through the tubes. Why is it better to use an inductor rather than a resistor for this purpose?

Short answer

It is better to use resistor instead of inductor in order to prevent power loses.

Step-by-step solution

Define energy in circuit

Inductor stores electromagnetic energy. This energy is due to presence of magnetic field inside inductor which generates due to alternating current supply by the ac power source. For example in inductor, electromagnetic energy is expressed as

$U_B=\frac{1}{2}L{l}^2$where $L$is the inductance and I is the current.

Resistor when connected in circuit despites heat or power loss as per joule’s law of heating which is mathematically expressed as

$H=l^{2}Rt$where $H$is the heat loss, $R$is the resistance and t is time for which current is flowing.

Why inductor is better.

Fluorescent light is operated on AC power supply most of the times. The energy which stores in inductor during first half cycle of AC supply, releases in other half cycle making the average dissipated power of inductor nearly zero.This greatly limits the loss in energy.

If resistor is used for this purpose then the energy will only keep on releasing in form of heat as per joule’s law stated above.The average dissipated power of resistor is not even close to zero which extends the waste of electricity.

Thus, inductor is use instead of resistor since it does not generate much heat.