Question

A body has a charge of -3.2μC . The number of excess electrons it has is

• A. 5.12×10²⁵
• B. 5×10¹²
• C. 2×10¹³
• D. 5.12×10¹³

Answer 1

The Correct Option is C

We are given the charge on the body as \( -3.2 \, \mu C \). The charge of a single electron is \( e = 1.6 \times 10^{-19} \, C \).

Step 1: Formula to calculate the number of excess electrons:

The number of excess electrons \( n \) is given by:

\[ n = \frac{\text{Charge}}{\text{Charge of 1 electron}} \]

Step 2: Calculation:

\[ n = \frac{-3.2 \times 10^{-6}}{1.6 \times 10^{-19}} = 2 \times 10^{13} \]

The number of excess electrons is \( 2 \times 10^{13} \), which corresponds to option (C).

Answer 2

The charge on one electron is \( e = 1.6 \times 10^{-19} \, \text{C} \).
The total charge is \( -3.2 \, \mu\text{C} = -3.2 \times 10^{-6} \, \text{C} \).
The number of excess electrons is given by: \[ n = \frac{|Q|}{e} = \frac{3.2 \times 10^{-6}}{1.6 \times 10^{-19}} = 5.12 \times 10^{13} \] Thus, the number of excess electrons is \( 5.12 \times 10^{13} \).