91Ó°ÊÓ

Electric charge is a basic property of matter that causes small objects to attract or repel each other. The charge is quantised in nature and the electronic charge is the basic unit of charge.

The net quantity of charge is given as:

\(Q = ne\) … (i)

Here, n is the number of electrons and e is the electronic charge.

The net charge accumulated by the person is, \(Q = - 28\;{\rm{\mu C}}\).

The charge on an electron is, \(e = 1.6 \times {10^{ - 19}}\;{\rm{C}}\)

From equation (i), the number of excess electrons is,

\(n = \frac{q}{e}\)

Substitute the values in the above expression.

\(\begin{aligned}{l}n = \frac{{ - 28 \times {{10}^{ - 6}}\;{\rm{C}}}}{{ - 1.6 \times {{10}^{ - 19}}\;{\rm{C}}}}\\n = 1.75 \times {10^{14}}\end{aligned}\)

Thus, the number of excess electrons is \(1.75 \times {10^{14}}\).

The expression to find the increase in mass is given as:

\(\Delta m = n \times {m_e}\)

Here, \({m_e}\)is the mass of the electron.

Substitute the values in the above expression.

\(\begin{aligned}{l}\Delta m = \left( {1.75 \times {{10}^{14}}} \right) \times \left( {9.1 \times {{10}^{ - 31}}\;{\rm{kg}}} \right)\\\Delta m = 1.59 \times {10^{ - 16}}\;{\rm{kg}}\end{aligned}\)

Thus, the mass of the person is increased by \(1.59 \times {10^{ - 16}}\;{\rm{kg}}\).