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===Example Calculations===
{| class="wikitable"
| style="height:20px; width:300px; text-align:center;" |An [[LED]] uses 842J over a period of 120 seconds. Calculate the '''power''' of the [[LED]] correct to two [[Significant Figures|significant figures]].
| style="height:20px; width:300px; text-align:center;" |A toaster uses 180kJ while toasting some bread for 1 [[minute]] and 27 [[second]]s. Calculate the '''power''' of the toaster correct to 2 [[Significant Figures|significant figures]].
|-
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities'''
W = 842J
t = 120s
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities'''
W = 180kJ = 180x10<sup>3</sup>J
t = 1min27s = 87s
|-
| style="height:20px; width:300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
<math>P=\frac{W}{t}</math>
<math>P=\frac{842}{120}</math>
<math>P=7.01616W</math>
<math>P\approx 7.0W</math>
| style="height:20px; width:300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
<math>P=\frac{W}{t}</math>
<math>P=\frac{180 \times 10^3}{87}</math>
<math>P=2068.9655W</math>
<math>P\approx 2100W</math>
|}
{| class="wikitable"
| style="height:20px; width:300px; text-align:center;" |A light bulb is supplied a current of 625mA. The [[Potential Difference|potential difference]] across the terminals on the [[Electrical Bulb|light bulb]] is 96 [[volt]]s. Calculate the [[power]] of the [[Electrical Bulb|bulb]] correct to two [[Significant Figures|significant figures]].