What is the name of the devices that senses the current flowing, tripping the circuit, and cutting off the electricity

The devises that sense the current flowing, tripping the circuitm and cutting off the electricity are the Ground Fault Circuit Interrupter (GFCI)

Explanation:

The ground fault circuit interrupter is a mechanism hat cuts the flux of energy after sensing a disbalance to prevent a negative effect on the electronic devices that are connected to the interrupter. They are meant to stop the flux of current because a lot of accidents relate persons causing that electricity disbalance and suffering a very hard hit in their body.

do u ahve any choices

u = 30

continuing your method

= +

subtract from both sides

= - thus

= -

= ⇒ u = 30