Answer
Potential difference across hands required for a lethal shock is $100 V$
Work Step by Step
Recall that resistance of a conductor is,
$$R=\frac{\rho l}{A}$$
The average resistivity of interior of the human body is taken as $0.5 Ωm$
Solving for $R$,
$R = \frac{0.5 Ωm \times 1.6m}{(π0.0025)m^{2}} \approx 1000Ω$
Recall the equation for potential difference across a circuit,
$$V=IR$$
$V= 100 mA \times 1000Ω = 100 V$
