Question

You hold a ruler that has a charge on its tip 6 cm above a small piece of tissue paper to see if it can be picked up. The ruler has - 12 μC of charge. The tissue has 3 g of mass. What is the minimum charge required to pick up the tissue paper?

Answer 1

Answer:

9.81 × 10⁻¹⁰ C

Explanation:

Given:

Distance between the tissue and the tip of the scale, r = 6 cm = 0.06 m

Charge on the ruler, Q = - 12 μC = - 12 × 10⁻⁶ C

Mass of the tissue = 3 g = 0.003 Kg

Now,

The force required to pick the tissue, F = mg

where, g is the acceleration due to gravity

also,

The force between (F) the charges is given as:

$F=\frac{kQq}{r^2}$

where,

q is the charge on the tissue

k is the Coulomb's constant = 9 × 10⁹ Nm²/C²

thus,

$mg=\frac{kQq}{r^2}$

on substituting the respective values, we get

$0.003\times9.81=\frac{9\times10^9\times(-12\times10^{-6})\times q}{0.06^2}$

or

q = 9.81 × 10⁻¹⁰ C

Minimum charge required to pick the tissue paper is 9.81 × 10⁻¹⁰ C