The current that did not return.

Why can a small leakage trip a device carrying a large load?

Setting up the mechanism…

Residual current: 0.00mA
Outgoing current before trip: 0.000A
Returning current before trip: 0.000A

Contacts: Closed

Fit the differential sensor and linked contacts

Why can a small leakage trip a device carrying a large load?

Live and neutral pass through one magnetic core in opposing directions. Equal currents cancel; their difference drives the trip mechanism even when the load current is ordinary.

Iresidual = |Ilive − Ineutral|

What this model simplifies

Illustrative 30 mA residual-current threshold, not a safety-device certification. This detects current imbalance rather than thermal overload; timing and different RCD waveform classes are omitted.

Read the source · openstax.org ↗

Put it to work.

Trip for 35 mA residual current while a balanced 10 A load remains connected.

Make it work.

Find when unequal return current trips the contacts.

Run

Fine adjustments 2

Load currentA

Residual currentmA

The current that did not return.

Why can a small leakage trip a device carrying a large load?

Loading the experiment…

Figuvo

Understand by doing.

Understanding is something you do.

Figuvo is a place to look inside everyday things, build a connection, and discover the idea behind them.

177 interactive experiments. Each has a working model and a challenge to test what you found.

The original inspiration

Levers & fulcrums The surprising gyroscope The field cannon Inside the human body

Original demonstrations by The Bugged Dev. The teaching models and interactions here are new implementations.

Community builds

New teaching models inspired by public builds shared around Anatomy.

Anatomy · the original announcement How a rocket pushes through space · Gustavo Inside a tactile key switch · @retaqib Pressure through the coffee bed · Gustavo The overbalance wheel · Shawn A seconds pendulum clock · @Baconbrix Three feet on the ground · Soju Inside a layered particle detector · Yash A double-deck pressure cabin · Charlie Leave the spent booster behind · @quantapar Principal, interest and escrow · Sean Gear a Martian year · @samani_Two balls in, two balls out · @samani_Two slits, one probability pattern · @samani_Join through a clear plastic cover · Josh Brown Lay pipe without a sharp bend · @Phi10w Eight cylinders and a blower · @love4hxns Four columns under a Joglo roof · Nur Asyrof An office for dependent tasks · Yaroslav Yablonski One image, six editable layers · Meng To The Redis caching machine · @uviii_03 Inside the Sony CMD-J5 · Ann Afterburner thrust stand · Joshua Guo Open-back headphones · Surajan Shrestha Two-thread lockstitch machine · @slashui Signal factory · Dhruval Golakiya

Everyday electrical

The current that did not return.

Why can a small leakage trip a device carrying a large load?

Setting up the mechanism…

Residual current: 0.00mA
Outgoing current before trip: 0.000A
Returning current before trip: 0.000A

Contacts: Closed

Fit the differential sensor and linked contacts

Why can a small leakage trip a device carrying a large load?

Live and neutral pass through one magnetic core in opposing directions. Equal currents cancel; their difference drives the trip mechanism even when the load current is ordinary.

Iresidual = |Ilive − Ineutral|

What this model simplifies

Illustrative 30 mA residual-current threshold, not a safety-device certification. This detects current imbalance rather than thermal overload; timing and different RCD waveform classes are omitted.

Read the source · openstax.org ↗

Put it to work.

Trip for 35 mA residual current while a balanced 10 A load remains connected.

Make it work.

Find when unequal return current trips the contacts.

Run

Fine adjustments 2

Load currentA

Residual currentmA