Transformer Physics Example 2

Follow the full solution, then compare it with the other examples linked below.

Example 2

medium
An ideal transformer steps down 11,000 V11{,}000 \text{ V} to 220 V220 \text{ V}. If the secondary current is 50 A50 \text{ A}, what is the primary current?

Solution

  1. 1
    For an ideal transformer, power is conserved: VpIp=VsIsV_p I_p = V_s I_s.
  2. 2
    Ip=VsIsVp=220×5011,000=11,00011,000=1 AI_p = \frac{V_s I_s}{V_p} = \frac{220 \times 50}{11{,}000} = \frac{11{,}000}{11{,}000} = 1 \text{ A}
  3. 3
    The step-down ratio is 50:150:1, so the current is stepped up by the same factor.

Answer

Ip=1 AI_p = 1 \text{ A}
In an ideal transformer, power in equals power out. When voltage is stepped down, current is stepped up by the same ratio. This is why high-voltage transmission uses low current.

About Transformer

A device that changes AC voltage using electromagnetic induction between two coils on a shared iron core.

Learn more about Transformer →

More Transformer Examples

Example 1 easy

A step-up transformer has [formula] turns on the primary coil and [formula] turns on the secondary c

Example 3 medium

A phone charger transformer converts [formula] AC to [formula] AC. If the primary coil has [formula]

Example 4 hard

A transformer with [formula] efficiency steps up [formula] to [formula]. If the secondary delivers [

← All Transformer Examples Transformer Concept

Related Concepts

Faraday's LawGenerator