Question

What is the ratio of the resistance if two bulbs have ratings of 40 W, 220 V & 20 W, 110 V

Answer 1

Answer :

$Ratio\;of\;the\;resistances\;of\;two\;bulbs\;= 2 : 1$

Given :-

$Power_1\;=40\;W$

$Potential\;difference_1\;=220\;V$

$Power_2\;=20\;W$

$Potential\;difference_2\;=110\;V$

To find :-

$Ratio\;of\;resistance\;of\;two\;bulbs$

Solution :-

$Power\;of\;a\;bulb\;(P)= \frac{V^2}{R}$

$For\;the\;first\;bulb :$

• $R_1\;=\frac{V^2_1}{P_1}$

• $R_1\;=\frac{220^2}{40}$

• $R_1\;=1210$ Ω

$For\;the\;second\;bulb :$

• $R_2\;=\frac{V^2_2}{P_2}$

• $R_2\;=\frac{110^2}{20}$

• $R_2\;=605$ Ω

$Ratio\;of\;resistances :$

• $R_1\;:R_2$

• $1210\;:605$

• $2\;:1$

∴ $Ratio\;of\;the\;resistances\;of\;two\;bulbs\;= 2 : 1$

Answer 2

Answer:

The ratio of their resistance is 4.

Similarly for bulb (b), P =40 W and V = 110 V. Thus, it is clear from the result the for bulb (a)has a higher resistance.

Explanation:

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