A circuit has a line of 5 A. How many lamps of rating 40W,220V can simultaneously run on this line safely ?

Explanation

`I = 5A` No. of lamps `=n` Power , `P = 40W`
`V=220 V`
Power of 1 bulb `=40 W` Power of n bulbs `= 40 n ` watts
`P = V xx I` `4n = 220 xx 5`
`implies n = ( 220 xx 5)/(40) = (55)/(2) = 27.5`
`:. `No . of lamps of `=27`