Why do the bulbs in the parallel circuit seem brighter?

Question

Why do the bulbs in the parallel circuit seem brighter even though the current flowing in the branches is less than the current flowing out from the source. Even though a series circuit all the current flowing goes to the same branch unlike the parallel circuit.

Answer 1

The bulbs in a parallel circuit work under the same voltage unlike the bulbs in a series circuit where the voltage gets divided among the bulbs. So the bulbs in the parallel circuit do actually glow brighter.

Answer 2

Let me explain with an example.

Consider two bulbs each of ratings 250 watt, 250 volt.

When they are connected in parallel across 250 volt line, full voltage appears across each bulb and current through ecah bulb is given by

Current = Power / voltage = 250 / 250 = 1 ampere.

The main line current will be 2 ampere which will divide into two parts with 1 ampere flowing through each bulb and giving an output of 250 watt in each bulb.

Now, consider that the same two bulbs are connected in series across 250 volt line. Here, resistance of filament of each bulb is

R = (voltage)^2 / power = (250)^2 / 250 = 250 ohm

Total resistance of 2 bulbs in series = 500 ohm

Current in the line = voltage / resistance = 250 / 500 = 0.5 amp.

Thus, main line current itself is one fourth of what it was in parallel connection and even though full main line current flows through each bulb, power output of each bulb is

(current)^2 x resistance

= (0.5)^2 x 250 = 62.5 watt

Thus, brightness of each bulb is one-fourth of what it is in parallel connection.

Answer 3

Two bulbs in parallel get the full voltage from the source and so glow at full brightness. Two bulbs in series only get half the voltage and so are only half as bright.