How does high internal resistance make high voltage power supplies safe?

[Aimhigh]

Homework Statement

When the internal resistance is large in comparison to the external resistance, the terminal potential difference falls to a small value. This is used to make high voltage supplies safe for use in a laboratory. Explain how this makes the supply safe.

Homework Equations

V_terminal = EMF - V_internal

The Attempt at a Solution

If the internal resistance is high, since V_internal = I r, where r is the internal resistance, the V_internal will be high. This means the V_terminal will be low. And because of the internal resistance, the current will also be low. So then what is the point of having a high voltage power supply?

 

[Aimhigh]

I have attached what I think is the solution. Please could you look at it and see if it makes sense and is right. Thanks