Question

If E = 7.50V and r=0.45Ω, find the minimum value of the voltmeter resistance RV for which the voltmeter reading is within 1.0% of the emf of the battery.

Answer 1

Answer:

The minimum value of the voltmeter resistance is 44.7 Ω

Explanation:

Given that,

Emf E= 7.50 V

Internal resistance r = 0.45 ohm

We need to calculate the voltmeter reading

$V=(100-1)\%\ of\ E$

$V=99\%\times V$

Put the value into the formula

$V=0.99\times7.50$

$V=7.425\ volt$

We need to calculate the current

Using formula of emf

$E=V+ir$

$ir=E-V$

$i=\dfrac{E-V}{r}$

Put the value into the formula

$i=\dfrac{7.50-7.425}{0.45}$

$i=0.166\ A$

We need to calculate the minimum value of the voltmeter resistance

Using ohm's law

$V=iR$

$R=\dfrac{V}{i}$

Put the value into the formula

$R=\dfrac{7.425}{0.166}$

$R=44.7\ \Omega$

Hence, The minimum value of the voltmeter resistance is 44.7 Ω