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A multipurpose transformer has a secondary coil with several points at which a voltage can be extracted, giving outputs of 5.60, 12.0, and 480 V. (a) The input voltage is 240 V to a primary coil of 280 turns. What are the numbers of turns in the parts of the secondary used to produce the output voltages? (b) If the maximum input current is 5.00 A, what are the maximum output currents (each used alone)?

Short Answer

Expert verified
The number of turns for outputs of 5.60 V, 12.0 V, and 480 V are 6.5, 14, and 560 turns respectively. The maximum output currents for these voltages are 214.29 A, 100 A, and 2.5 A respectively.

Step by step solution

01

Calculate turns for 5.60 V output

Use the transformer equation \( V_p / V_s = N_p / N_s \) where \( V_p = 240 \) V, \( V_s = 5.60 \) V, and \( N_p = 280 \) turns. Solve for \( N_s \): \( N_s = (N_p \times V_s) / V_p \) to get the number of turns for 5.60 V output.
02

Calculate turns for 12.0 V output

Repeat the transformer equation for the 12.0 V case: \( N_s = (N_p \times V_s) / V_p \) where \( V_s = 12.0 \) V.
03

Calculate turns for 480 V output

Use the transformer equation for the 480 V case: \( N_s = (N_p \times V_s) / V_p \) where \( V_s = 480 \) V.
04

Calculate maximum output current for 5.60 V

Use the power conservation equation \( P_p = P_s \) which implies that \( V_p \times I_p = V_s \times I_s \) where \( I_p = 5.00 \) A. Solve for \( I_s \) to find the maximum output current for the 5.60 V output.
05

Calculate maximum output current for 12.0 V

Repeat the power conservation calculation for the 12.0 V output to find \( I_s \) for that voltage.
06

Calculate maximum output current for 480 V

Repeat the power conservation calculation for the 480 V output to find \( I_s \) for that voltage.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Transformer Equation
Understanding the transformer equation is crucial for grasping how transformers work. This equation relates the voltage and number of turns in the primary coil (\(V_p, N_p\)) to the voltage and number of turns in the secondary coil (\(V_s, N_s\)). It's given by the formula: \( V_p / V_s = N_p / N_s \).

Using this equation, we can determine the characteristics of the transformer based on its design. For example, if you know the input voltage and the number of turns in the primary coil, as well as the desired output voltage, you can calculate the number of turns needed in the secondary coil to achieve that output voltage. This concept is used often in designing electrical circuits that need different voltages.
Electrical Transformers
Electrical transformers are devices that transfer electrical energy between two or more circuits via electromagnetic induction. Transformers are principally used to increase (called 'step up') or decrease ('step down') voltage levels between circuits.

The core concept behind a transformer consists of two sets of coils, the primary and secondary, wound around a magnetic core. When an alternating current flows through the primary coil, it creates a varying magnetic field, which induces a voltage in the secondary coil. The transformation of the voltage depends on the ratio of turns between the primary and secondary coils. The efficiency of a transformer is high, making it ideal for a wide variety of applications, from power distribution to adjusting voltage levels in electronic devices.
Voltage Conversion Physics
Voltage conversion in transformers is based on the principle of electromagnetic induction. When a varying electric current flows through the primary coil, it creates a time-varying magnetic field. This changing magnetic field induces an electromotive force (EMF) across the secondary coil, according to Faraday's Law of Induction.

For voltage conversion, a key factor is the turn ratio of the transformer. This ratio determines how the voltage is altered. For example, if a transformer has a turn ratio of 1:10, it means that for every turn on the primary coil, there are 10 turns on the secondary coil, which typically results in a higher voltage output. The physical basis for this is rooted in the interplay between the magnetic field strength, the number of turns of the coil, and the rate at which the magnetic field changes.
Current and Power Conservation
Current and power conservation in transformers are based on the Law of Conservation of Energy, which states that energy cannot be created or destroyed - only transformed from one form to another. For an ideal transformer, the power input on the primary side must equal the power output on the secondary side, ignoring any losses. The power conservation equation \( P_p = P_s \) equates the product of voltage and current on the primary side (\(V_p \times I_p\)) to that on the secondary side (\(V_s \times I_s\)).

Therefore, if we step up the voltage from primary to secondary coil, the current will decrease proportionately on the secondary side to keep the power consistent. Likewise, if we step down the voltage, the current will increase. Understanding this relationship helps in designing circuits that are safe and effective for the given application.

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