# Several Electric Bulbs Designed to Be Used on a 220 V Electric Supply Line, Are Rated 10 W. How Many Lamps Can Be Connected in Parallel with Each Other Across the Two Wires of 220 - Science

Sum

Several electric bulbs designed to be used on a 220 V electric supply line, are rated 10 W. How many lamps can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A?

#### Solution

Resistance R1 of the bulb is given by the expression,
Supply voltage, V = 220 V
Maximum allowable current, I = 5 A
Rating of an electric bulb P=10watts
Because R=V2/P

R_1=(220)^2/10=4840

According to Ohm's law

V=IR

Let R is the total resistance of the circuit for x number of electric bulbs

R=V/I

=220/5=44Omega

Resistance of each electric bulb, R1=4840Ω

1/R=1/R_1+1/R_2+.......Upto x times

1/R=1/Rxx x

x=R_1/R=4840/44=110

∴ Number of electric bulbs connected in parallel are 110.

Concept: System of Resistors - Resistances in Parallel
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#### APPEARS IN

NCERT Class 10 Science
Chapter 12 Electricity
Q 12 | Page 221