Question

A 50ve change flow through a conductor if the p.d between it end 20mv find the work done by the change 

Answer 1

By definition, the work done by charge is given as:

$$W = -Uq$$

where $U = 20mV =0.02V$ is the potential difference, and

$$q = 50ve = 50\cdot 1.6\times 10^{-19}C = 8\times 10^{-18}C$$

is the charge ($1.6\times 10^{-19}C$ is the elementary charge). Thus, obtain:

$$W = -0.02V\cdot 8\times 10^{-18}C = -1.6\times 10^{-19}J$$

Answer. $-1.6\times 10^{-19}J$.