Update energy measurement (#134)

Update content and question related to energy measurement in line with #127

docs/energy-efficiency.mdx

@@ -48,10 +48,10 @@ Clean energy comes from renewable, zero-emission sources that do not pollute the
 
 ### Energy measurement
 
-- Energy is measured in joules (J). Joules measure the volume of energy.
-- Watt (W) is a rate, corresponding to one joule per second.
-- A kilowatt (kW) is therefore also a rate, corresponding to 1000 joules per second.
-- A kilowatt-hour (kWh), is a measure of energy (J) corresponding to one kilowatt of power sustained for one hour.
+- Energy is measured in joules (J), the [SI](https://en.wikipedia.org/wiki/International_System_of_Units) unit of energy.
+- Power is measured in watts, where 1 watt (W) is a rate corresponding to one joule per second.
+- A kilowatt (kW) is, therefore, also a rate corresponding to 1000 joules per second.
+- A kilowatt-hour (kWh) is a measure of energy (J) corresponding to one kilowatt of power sustained for one hour.
 
 ## How to improve energy efficiency
 
@@ -162,7 +162,7 @@ Servers are usually not configured for aggressive or even minimal power saving.
       ],
     },
     {
-      question: "What unit measures volume of energy?",
+      question: "What is the SI unit of energy?",
       answers: [
         {
           text: "Watts",
@@ -173,7 +173,7 @@ Servers are usually not configured for aggressive or even minimal power saving.
           isCorrect: false,
         },
         {
-          text: "Kilowatt-hours",
+          text: "Joules",
           isCorrect: true,
         },
       ],