How is brightness affected by batteries and bulbs connected in series?

In this video, I shared a method to help students remember how the brightness in each light bulb is affected by batteries and bulbs connected in series. This topic is in the theme Systems, Upper Block Science.
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Opening and ending music pieces by Lynn Koo.
https://soundcloud.com/lynnkoo

Click below for a circuit construction simulation kit.

Click to Run

Household Energy Consumption in kWh

Why is the joule not used as a unit of the total electrical energy used in an average household?

Joule is a very small unit for household electrical consumption and the numbers will become very large for calculation. It will be more convenient to calculate total electrical energy used in an average household using kWh.

Check out this BBC - GCSE Bitesize link on Practical Electricity - using kWh for household energy consumption.