Why are transformers used?

Summary

This script explains the necessity of step-up and step-down transformers in electrical power transmission. Power stations often produce high voltages like 12,000 volts, but homes require lower voltages, typically between 120 and 240 volts. To minimize energy loss over long distances, the voltage is increased to around 400,000 volts using a step-up transformer. As the power approaches towns, a step-down transformer reduces it to 11,000 volts for local distribution, and further down to 240 volts for home use. The script also touches on the three-wire system in North America that allows for variable home voltages and contrasts it with the simpler two-wire system used in most of the world, which provides higher power to outlets.

Takeaways

• 🔌 Step Up Transformers: Used to increase voltage at the output, which is essential for long-distance transmission of electricity.
• 🔌 Step Down Transformers: Decrease voltage for local distribution and home use, ensuring safety and compatibility with household appliances.
• 🏠 Voltage Requirements: Homes typically require between 120 and 240 volts, contrasting with the much higher voltages produced by power stations.
• ⚡ Energy Loss: High voltage reduces current, which in turn minimizes energy loss due to resistance in the transmission cables.
• 🌐 Transmission Efficiency: Higher voltages allow for more efficient power transmission over long distances with reduced losses.
• 🔢 Ohm's Law Application: The script explains how resistance and current affect energy loss, using Ohm's Law to illustrate the point.
• 🌎 Voltage Variation: North American homes can have 120 or 240 volts due to a three-wire system, while most of the world uses around 230 volts with a simpler two-wire system.
• 🔑 Voltage Flexibility: The three-wire system in North America allows for half or full use of the secondary coil to achieve different voltage levels.
• 💡 Electrical Design: The two-wire system is simpler and can deliver more power to outlets, useful for high-power appliances like water kettles.
• 📚 Previous Content: The speaker references previous videos on residential electrical systems for further learning.
• 📱 Social Media Engagement: The script encourages following on various social media platforms and a website for more engineering content.

Q & A

What is the purpose of a step-up transformer?

A step-up transformer is used to increase the voltage on the output, which is beneficial for reducing energy loss during transmission over long distances by decreasing the current that needs to flow through the cables.

What is the purpose of a step-down transformer?

A step-down transformer is used to decrease the voltage on the output to a level suitable for local distribution and residential use, such as reducing it from high transmission voltages to around 240 volts for home use.

Why do we need to decrease the voltage from a power station to our homes?

The voltage produced by a power station is typically much higher than what is needed for home use. Decreasing the voltage ensures safety and efficiency in power distribution and use.

What is the typical voltage range needed for homes?

Homes typically require a voltage between 120 and 240 volts, depending on the region and the electrical system in use.

How does increasing voltage with a transformer reduce energy loss in cables?

By increasing the voltage, the current through the cable is reduced. Since energy loss in a cable is proportional to the square of the current, a higher voltage results in significantly lower energy loss.

Why is a higher voltage used for long-distance power transmission?

Higher voltages are used for long-distance transmission because they allow for the same amount of power to be transmitted with less current, thus reducing the energy loss due to the cable's resistance.

What is the typical voltage used for long-distance transmission after a step-up transformer?

The typical voltage used for long-distance transmission after a step-up transformer can be as high as 400,000 volts, which helps in reducing energy losses over long distances.

How does the three-wire system in North America allow for both 120 and 240 volts?

The three-wire system in North America uses an additional wire connected to the center of the secondary coil of the transformer, allowing the use of half or the full coil to achieve either 120 or 240 volts.

What is the main difference between the electrical systems in North America and most of the rest of the world?

In North America, a three-wire system is used, which allows for both 120 and 240 volts, while most of the world uses a two-wire system with a standard voltage around 230 volts.

Why is a two-wire system considered simpler and more efficient for power distribution?

A two-wire system is simpler because it does not require an additional wire for the center tap of the transformer coil. It also allows more power to be delivered to the outlets, making it useful for high-power applications like boiling water quickly.

How does the resistance of a cable affect energy loss during transmission?

The energy loss in a cable is directly proportional to the resistance of the cable and the square of the current flowing through it. Higher resistance and higher current result in greater energy loss.