Question

An electroscope has a charge of −2.0 µC while your finger has a charge of 2.7 µC. You touch the electroscope with your finger and discover that the charges of your finger and the electroscope are now the same. In this process, electrons were transferred from the electroscope to your finger. How many electrons were transferred in order for your finger and the electroscope to have the same charge?

Answer 1

Answer:

1.39 × 10⁻¹³ electrons were transferred

Explanation:

Given:

Charge on electroscope = - 2.0 μC

charge on finger = 2.7 μC

Now,

The net charge when in contact

= Charge on electroscope + charge on finger

or

The net charge when in contact = - 2.0 μC + 2.7 μC = 0.7 μC

Also,

Charge on the electroscope and the finger is same

thus,

The charge on the electroscope = $\frac{\textup{Net charge}}{\textup{2}}$

or

The charge on the electroscope = $\frac{0.7}{\textup{2}}$

or

The charge on the electroscope = 0.35 μC

Now,

The change in charge on the electroscope

= Final charge - Initial charge on the electroscope

= 0.35 μC - (- 2.0 μC)

or

The change in charge on the electroscope = 2.35 μC

also,

Charge = Number of electrons × Charge on an electron

or

2.35 μC = Number of electron  × 1.69 × 10⁻¹⁹ C

or

2.35 × 10⁻⁶ C = Number of electron  × 1.69 × 10⁻¹⁹ C

or

Number of electron = $\frac{\textup{2.35\times10^{-6}}}{\textup{1.69\times10^{-19}}}$

or

Number of electron = 1.39 × 10⁻¹³ electrons were transferred.