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===About Transformers===
: '''Transformers''' use a coil of [[wire]] in one [[circuit]] (primary coil) wrapped around a [[Soft Iron|soft iron]] core and second coil of [[wire]] in another [[circuit]] (secondary coil). When an [[Alternating Current|alternating current]] passes through the primary coil this creates a changing [[Magnetic Field|magnetic field]] which induces an alternating [[Potential Difference|potential difference]] across the secondary coil. If that secondary coil is connected in a [[circuit]] it will produce an [[Alternating Current|alternating current]].
: There are two types of '''transformer''' you should know:
:*Step Up '''Transformer''' - A '''transformer''' which increase the [[Potential Difference|potential difference]].
:*Step Down '''Transformer''' - A '''transformer''' which decrease the [[Potential Difference|potential difference]].
: Step up '''transformers''' are used in the [[National Grid]] to increase the [[Potential Difference|potential difference]] and decrease the [[Electrical Current|current]] for long distance transmission.
{| class="wikitable"
|-
| style="height:20px; width:200px; text-align:center;" |This [[diagram]] of a '''transformer''' shows that an [[Alternating Current|alternating current]] in the primary coil induces an alternating [[Potential Difference|potential difference]] in the secondary coil.
|}
===Equation===
''NB: You must be able to use this equation, but you do not need to remember it.''
(Primary Potential Difference)/(Secondary Potential Difference)=(Primary Coils)/(Secondary Coils)
<math>\frac{V_p}{V_s} = \frac{n_p}{n_s}</math>
<math>V_p</math> = The [[Potential Difference|potential difference]] across the primary coil.
<math>V_s</math> = The [[Potential Difference|potential difference]] across the secondary coil.
<math>n_p</math> = The number of loops on the primary coil.
<math>n_s</math> = The number of loops on the secondary coil.
===Example Calculations===
{| class="wikitable"
|[[File:TransformerQ1.png|center|300px]]
|[[File:TransformerQ2.png|center|300px]]
|-
| style="height:20px; width: 300px; text-align:center;" |Calculate the [[Potential Difference|potential difference]] across the secondary coil.
| style="height:20px; width: 300px; text-align:center;" |Calculate the [[Potential Difference|potential difference]] across the secondary coil.
|-
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in [[SI Unit]]s.'''
<math>V_p</math> = 3V
<math>n_p</math> = 4 coils
<math>n_s</math> = 8 coils
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in [[SI Unit]]s.'''
<math>V_p</math> = 9V
<math>n_p</math> = 6 coils
<math>n_s</math> = 8 coils
|-
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
<math>\frac{V_p}{V_s} = \frac{n_p}{n_s}</math>
<math>\frac{3}{V_s} = \frac{4}{8}</math>
<math>\frac{3}{V_s} = 0.5</math>
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
<math>\frac{V_p}{V_s} = \frac{n_p}{n_s}</math>
<math>\frac{9}{V_s} = \frac{6}{8}</math>
<math>\frac{9}{V_s} = 0.75</math>
|-
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
<math>0.5 \times V_s = 3</math>
<math>V_s = 6V</math>
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
<math>0.75 \times V_s = 9</math>
<math>V_s = 12V</math>
|}