Grounding and Protection Activity

Construction Context

TwoGuysOnPoleOne of the major features of distributing electricity around your home (or school or work) is doing it safely.  In the Insulation activity (http://theselsproject.org/insulation-activity/) and the Circuit Breaker Panel activity (http://theselsproject.org/circuit-breaker-panel-activity/) you learned about the role of these design elements for protection.  Another principle of electrical distribution associated with protection is something called grounding.  Electrical energy is moving electric charges.  Thunderstorm activity can cause a build-up of electrical charge, which has an attractive force with the earth or ground.  When the force is great enough, the charge connects with the ground in the form of lightening.  Electric current in the home has an attraction with ground.

The design of house circuits is for the electricity to flow from the circuit breaker panel to the appliance, say a food mixer in the kitchen then back to the breaker panel to the ground.  See the Circuit Breaker Panel activity mentioned above for an understanding of where this connection to the ground is located in your home.  If something goes wrong with the wiring in the appliance, the electrical energy may seek another pathway to the ground.  That is where the design of the appliance and electrical circuitry in the home work together to protect YOU from becoming the pathway to ground for the electricity.

One reason for learning about electricity in school science or technology classes is because these ideas are directly useful in your life now!  Understanding how electricity is generated, distributed, and used inside a home, school, or work can be of great benefit to you now!  This knowledge can keep you safe, keep things working, and perhaps be knowledge useful in a job, earning you more money.

Activity Description
This Grounding & Conduit document (downloadable here: http://theselsproject.org/wp-content/uploads/2013/04/Grounding-Conduit.pdf) will guide you through two activities that you can repeat in various ways around your house or at school. These demonstrate how the outside casing of certain appliances or structures in your home connects to ground. So if the wiring inside ever touches the outside, the pathway to ground will not be through YOU but through the third prong on the plug into the wall.  Finding out what parts of things are electrically connected can be quite remarkable.

Science Concepts
The circuit is completed when terminals are connected together and will not be complete if not connected.

Next Generation Science Standards
Scientific and Engineering Practices:
– Planning and carrying out investigations
– Constructing explanations and designing solutions

Crosscutting concepts:
– Energy and matter: Flows, cycles and conservation

Discussion Questions

  1. What would happen if you cut off the third prong on a plug and electrical energy from the inside of appliance (for example, your computer) touched the outside casing?
  1. From the activities in this section of SELS, diagram the pathway of electricity from the circuit breaker panel to the kitchen mixer back to the circuit breaker panel to ground. Make the diagram fit your house tracing each connection through the walls.
  1. Ask the power company representative to explain how grounding works in the distribution of electrical energy to your community.

  1. Investigate what special grounding protection is provided in the case of a lightning strike sending a surge to your home.

(Download the activity in PDF, Word)