Chapter 3: Electricity

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How many 176 Ω resistors (in parallel) are required to carry 5 A on a 220 V line?


Let the number of resistances be n.

The equivalent resistance of the resistors when connected in parallel is given by,

frac{1}{R} = frac{1}{176} + frac{1}{176} + frac{1}{176} ......n times

frac{1}{R} = frac{1 + 1 + 1 +.....n times}{176}

frac{1}{R} = frac{n}{176}

R = frac{176}{n} Omega

It is given that,

V = 220 V

I = 5 A

Now, using Ohm’s law

V = IR

R = frac{V}{I}

frac{176}{n} = frac{220}{5}

n = frac{176 	imes 5}{220}

n = frac{176}{44}

n = 4

Hence, four resistance of 176 Ω is required to draw the 5 A current when connected across the 220 V line.

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