Question

A $2.5V$ battery is connected across a resistor of $500\Omega .$ If the battery voltage is charged to $5V,$ what should be the value of the resistance connected in series with $500\Omega$ so that it draws the same amount of current?

• A. $500\Omega$
• B. $750\Omega$
• C. $1000\Omega$
• D. $1250\Omega$

Answer 1

The correct option is A $500\Omega$

$I=\frac{2.5}{500}=5\times {10}^{-3}A$

$I=\frac{5}{500+R}$

$5\times {10}^{-3}=\frac{5}{500+R}$

$5\times {10}^{-3}\times 500+5\times {10}^{-3}\times R=5$

$R=\frac{1-0.5}{{10}^{-3}}$

$=0.5\times {10}^3$

$R=500\Omega$