Summary
Highlights
Introduction to Transformers00:00:02
Transformers change the potential difference of electricity. There are two main types: step-up and step-down, used in the National Grid. Both consist of two coils of wire around an iron core.
Step-Up and Step-Down Transformers00:00:16
In a step-up transformer, voltage is increased, with fewer turns on the primary coil than the secondary. In a step-down transformer, voltage is decreased, with more turns on the primary coil than the secondary.
How Transformers Work: Electromagnetic Induction00:00:31
Transformers work via electromagnetic induction. An AC current in the primary coil generates an alternating magnetic field in the iron core, which then induces a potential difference in the secondary coil at the same frequency. This only works with AC current.
Formulas for Potential Difference00:01:03
The potential difference can be calculated using the formula: (potential difference across primary coil) / (potential difference across secondary coil) = (number of turns on primary coil) / (number of turns on secondary coil). An example is provided to illustrate this.
Power and Current in Transformers00:01:34
Transformers are nearly 100% efficient, meaning power in equals power out. This provides another formula: (current in primary coil × potential difference across it) = (current in secondary coil × potential difference across it). An example calculation is shown.
Switch-Mode Transformers00:02:10
Switch-mode transformers are found in laptop and mobile phone chargers. They operate at high frequencies (50-200 kHz) and consume very little power when the device is not plugged in.