Materi Kemagnetan Kelas 9 (Part-6) Transformator

Summary

This educational video explores the principles of transformers, focusing on how they alter voltage and current in AC circuits. It explains the roles of the primary and secondary coils, introduces the concepts of step-up and step-down transformers, and presents key mathematical relationships between voltage, current, and windings. The video also includes practical examples and problems to calculate secondary voltage, current, and transformer efficiency. With a clear breakdown of formulas and practical tips, this content serves as an accessible guide to understanding transformer functionality and solving related problems.

Takeaways

• 😀 Transformers are devices used to increase or decrease voltage in an electrical circuit.
• 😀 A transformer consists of an iron core and coils, with one coil connected to an AC power source (primary) and the other connected to the electrical device (secondary).
• 😀 The voltage in the primary coil is called primary voltage (Vp), and the voltage in the secondary coil is called secondary voltage (Vs).
• 😀 The relationship between the primary and secondary coils is governed by the formula: NP/NS = VP/VS = IS/IP.
• 😀 Transformers can be categorized into two types: step-up transformers (which increase voltage) and step-down transformers (which decrease voltage).
• 😀 In a step-up transformer, the primary coil has fewer turns than the secondary coil, leading to higher secondary voltage and lower secondary current.
• 😀 In a step-down transformer, the primary coil has more turns than the secondary coil, resulting in lower secondary voltage and higher secondary current.
• 😀 The power (P) in a transformer is related to the voltage (V) and current (I) with the formula: P = V × I.
• 😀 Efficiency of a transformer can be calculated using the formula: Efficiency = (VS × IS) / (VP × IP) × 100%, though it is always less than 100% due to energy loss in the form of heat.
• 😀 The script includes example problems on calculating transformer voltages, currents, and the efficiency of transformers, providing practical applications of the formulas discussed.

Q & A

What is a transformer, and what is its purpose?

A transformer is a device used to either increase or decrease the voltage of alternating current (AC) electricity. It consists of a core and two windings, known as the primary and secondary coils. The primary coil is connected to the AC source, and the secondary coil is connected to the electrical device.

What is the difference between the primary and secondary windings of a transformer?

The primary winding is connected to the AC source, and the secondary winding is connected to the electrical load or device. The primary coil receives the incoming voltage, while the secondary coil delivers the transformed voltage to the device.

What is the relationship between the primary and secondary voltages in a step-up transformer?

In a step-up transformer, the number of primary coils is fewer than the number of secondary coils. As a result, the primary voltage is lower than the secondary voltage, meaning the transformer increases the voltage.

How are current and voltage related in a transformer?

Current and voltage in a transformer are inversely related. When the voltage increases (as in a step-up transformer), the current decreases, and when the voltage decreases (as in a step-down transformer), the current increases.

What formula can be used to relate the number of coils (windings), voltage, and current in a transformer?

The formula that relates the number of windings (N), voltage (V), and current (I) is: NP/NS = VP/VS = IP/IS. This means that the ratio of primary to secondary windings equals the ratio of primary to secondary voltage, and also the inverse ratio of primary to secondary current.

What is the main feature of a step-down transformer?

In a step-down transformer, the number of primary coils is greater than the number of secondary coils. This results in a higher primary voltage and a lower secondary voltage, while the current in the secondary coil increases relative to the primary coil.

How can you calculate the voltage in the secondary coil of a transformer if you know the primary voltage and the number of coils?

To calculate the secondary voltage (VS), use the formula: NP/NS = VP/VS. Rearranging it, VS = VP * NS / NP, where VP is the primary voltage, NP is the number of primary coils, and NS is the number of secondary coils.

In the example provided, what is the secondary voltage when the primary voltage is 240V, and the number of coils in the primary and secondary are 6000 and 200, respectively?

Using the formula NP/NS = VP/VS, the secondary voltage (VS) is calculated as 240 * 200 / 6000, which results in 8 volts.

What is the formula to calculate the efficiency of a transformer?

The efficiency of a transformer is given by the formula: Efficiency = (VS * IS) / (VP * IP) * 100%. This measures the percentage of the energy transferred from the primary coil to the secondary coil.

If a transformer has an efficiency of 60%, a secondary voltage of 50V, and a current of 4A, what is the primary current when the primary voltage is 200V?

To find the primary current (IP), we use the efficiency formula: 60 = (50 * 4) / (200 * IP) * 100%. Solving this, we find that IP = 1.67A.