Very important question:
Two bulbs of 40W and 60W are connected in series with an AC power supply of 100V. Which bulb will glow brighter and why?
Ans:
1. When connected in series: In a series connection, current flowing across each element is same. So when 40W bulb and 60W bulb are connected in series, same current will flow through them. To find which bulb will glow brighter we need to find the power dissipation across each of them. From the relation
P=(I*I) R
since current is same we can say that power dissipation will be higher for the bulb with higher resistance i.e. 40W bulb.
Hence 40W bulb will glow brighter in series connection.
2. When connected in parallel: In a parallel connection, voltage across each element is same. So when 40W bulb and 60W bulb are connected in parallel, voltage across them will be same (100 V in the given case). To find which bulb will glow brighter we need to find the power dissipation across each of them. From the relation
P=(V*V)/R
since voltage is same we can say that power dissipation will be higher for the bulb with lower resistance i.e. 60W bulb.
Hence 60W bulb will glow brighter in parallel connection.
NOW HOW TO REMEMBER THIS-
***At our homes, loads (such as bulbs) are connected in parallel and you always see that higher rated bulb glows more brightly i.e 100W bulb glows more brightly than 60W bulb or 40W bulb.
***So always remember if bulbs are connected in parallel, the bulb with higher rated power will glow brighter and if they are connected in series, the bulb with lower rated power will glow brighter.
Two bulbs of 40W and 60W are connected in series with an AC power supply of 100V. Which bulb will glow brighter and why?
Ans:
1. When connected in series: In a series connection, current flowing across each element is same. So when 40W bulb and 60W bulb are connected in series, same current will flow through them. To find which bulb will glow brighter we need to find the power dissipation across each of them. From the relation
P=(I*I) R
since current is same we can say that power dissipation will be higher for the bulb with higher resistance i.e. 40W bulb.
Hence 40W bulb will glow brighter in series connection.
2. When connected in parallel: In a parallel connection, voltage across each element is same. So when 40W bulb and 60W bulb are connected in parallel, voltage across them will be same (100 V in the given case). To find which bulb will glow brighter we need to find the power dissipation across each of them. From the relation
P=(V*V)/R
since voltage is same we can say that power dissipation will be higher for the bulb with lower resistance i.e. 60W bulb.
Hence 60W bulb will glow brighter in parallel connection.
NOW HOW TO REMEMBER THIS-
***At our homes, loads (such as bulbs) are connected in parallel and you always see that higher rated bulb glows more brightly i.e 100W bulb glows more brightly than 60W bulb or 40W bulb.
***So always remember if bulbs are connected in parallel, the bulb with higher rated power will glow brighter and if they are connected in series, the bulb with lower rated power will glow brighter.
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