Current Electricity Question 24
Question 24 - 2024 (31 Jan Shift 2)
By what percentage will the illumination of the lamp decrease if the current drops by $20 \%$ ?
(1) $46 \%$
(2) $26 \%$
(3) $36 \%$
(4) $56 \%$
Show Answer
Answer: (3)
Solution:
$P=i^{2} R$
$P _{\text {int }}=I _{\text {int }}^{2} R$
$P _{\text {final }}=\left(0.8 I _{\text {int }}\right)^{2} R$
$%$ change in power $=$
$\frac{P _{\text {final }}-P _{\text {int }}}{P _{\text {int }}} \times 100=(0.64-1) \times 100=-36 \%$
