Series and parallel connection of Bulbs

Question

when a 200W, 400W, and 1000W bulbs are connected in series across a main of the three, the bulb which glows brightest is the 200W and not 1000W. What is the reason ?

 

Answer 1

You can get the answer by using OHM's law and the electrical power formula to the circuit and the assumption they are connected to 120 volts to get the numbers I got below. But if you use a different voltage you will get to the same conclusion.

 

Some calculations show that the 1000W bulb is designed to optimally work with a current of 8.3 Amperes (A), the 400W with 3.3 A and the 200W with 1.6 A.

 

When you connect the 3 bulbs in series the total current in the circuit goes down to 1 A aprox.

 

As you can see the 200W is the one that suffers the least decrease in optimal current from 1.6 A to 1 A as compared to the 1000W from 8.3 A to 1 A.

Answer 2

Because of the power law.

 

P = VI

 

P = V(V / R)

 

P = V² / R

 

In a series circuit, the current is the same throughout the entire loop.  But the voltage and power are inversely proportional to each other, if you manipulate the formula.  The lesser the power of the bulb, the greater the resistance on that bulb.  Because of this, the bulb will overheat and that overheating indicates a brighter glow.