19,879
edits
Changes
→Example Calculations
===Example Calculations===
====Finding Resistance from Current and Potential Difference====
{| class="wikitable"
|-
<math> R \approx 390 \Omega</math>
|}
====Finding Current from Potential Difference and Resistance====
{| class="wikitable"
| style="height:20px; width:300px; text-align:center;" |A [[Potential Difference|potential difference]] of 9.9V is placed across an 19 Ohm [[Electrical Resistor|resistor]]. Calculate the '''current''' flowing through the [[Electrical Resistor|resistor]] correct to two [[Significant Figures|significant figures]].
| style="height:20px; width:300px; text-align:center;" |A toaster has a [[Electrical Resistance|resistance]] of 27 Ohms is plugged into the [[Mains Electricity|mains]] which has a [[Potential Difference|potential difference]] of 230V. Calculate the current flowing through the toaster correct to two [[Significant Figures|significant figures]].
|-
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
V = 9.9V
R = 19Ω
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
V = 230V
R = 27Ω
|-
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
<math>R = \frac{V}{I}</math>
<math>19=\frac{9.9}{I}</math>
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
<math>R = \frac{V}{I}</math>
<math>27=\frac{230}{R}</math>
|-
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
<math>I=\frac{9.9}{19}</math>
<math>I=0.52105A</math>
<math>I\approx0.52A</math>
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
<math>I=\frac{230}{27}</math>
<math>I=8.519A</math>
<math>I\approx8.5A</math>
|}