Electromagnetic Effects Continued
Resumen
Send a current through a wire that sits in a magnetic field and the wire is pushed sideways. Wind that wire into a coil and the push becomes a spin: this is how every electric motor turns. Pair two coils on an iron core and a changing current in one induces a voltage in the other, which is how transformers raise and lower the voltages that power the world.
In this lesson you will describe the force on a current-carrying conductor and how reversing the current or field reverses it, find force directions and deflect charged particles, explain the turning effect on a coil and the d.c. motor with its commutator, and work through transformers from construction to the turns equation, the efficiency equation, and why high-voltage transmission cuts the power lost as \(I^2R\) heating in cables.
Objetivos
- Describe an experiment to show that a force acts on a current-carrying conductor in a magnetic field, including the effect of reversing: (a) the current (b) the direction of the field
- Know that a current-carrying coil in a magnetic field may experience a turning effect and that the turning effect is increased by increasing: (a) the number of turns on the coil (b) the current (c) the strength of the magnetic field
- Describe the construction of a simple transformer with a soft-iron core, as used for voltage transformations
- Use the terms primary, secondary, step-up and step-down
- Recall and use the equation Vₚ / Vₛ = Nₚ / Nₛ where p and s refer to primary and secondary
- Describe the use of transformers in high- voltage transmission of electricity
- State the advantages of high-voltage transmission
- [Supplement] Recall and use the relative directions of force, magnetic field and current
- [Supplement] Determine the direction of the force on beams of charged particles in a magnetic field
- [Supplement] Describe the operation of an electric motor, including the action of a split-ring commutator and brushes
- [Supplement] Explain the principle of operation of a simple iron-cored transformer
- [Supplement] Recall and use the equation for 100% efficiency in a transformer I V = I V p p s s where p and s refer to primary and secondary
- [Supplement] Recall and use the equation P = I2R to explain why power losses in cables are smaller when the voltage is greater
Nota de la lección
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Evaluación de la lección
Felicitaciones por completar la lección del Electromagnetic Effects Continued. Ahora que has explorado el conceptos e ideas clave, es hora de poner a prueba tus conocimientos. Esta sección ofrece una variedad de prácticas Preguntas diseñadas para reforzar su comprensión y ayudarle a evaluar su comprensión del material.
Te encontrarás con una variedad de tipos de preguntas, incluyendo preguntas de opción múltiple, preguntas de respuesta corta y preguntas de ensayo. Cada pregunta está cuidadosamente diseñada para evaluar diferentes aspectos de tu conocimiento y habilidades de pensamiento crítico.
Utiliza esta sección de evaluación como una oportunidad para reforzar tu comprensión del tema e identificar cualquier área en la que puedas necesitar un estudio adicional. No te desanimes por los desafíos que encuentres; en su lugar, míralos como oportunidades para el crecimiento y la mejora.
- The force on a current-carrying wire in a magnetic field is reversed by A. increasing the current B. reversing the current direction C. using a longer wire D. switching off the current Answer: B
- Fleming's left-hand rule gives the direction of the A. magnetic field B. induced current C. force on the wire D. e.m.f. Answer: C
- A transformer with 200 primary turns and 50 secondary turns is a A. step-up transformer B. step-down transformer C. d.c. transformer D. rectifier Answer: B
- A transformer has Vp = 240 V, Vs = 12 V and Np = 1000 turns. Ns equals A. 20 B. 50 C. 200 D. 2000 Answer: B
- Electricity is transmitted at high voltage mainly to A. increase the current B. reduce the power lost as heat in the cables C. change a.c. to d.c. D. raise the resistance of the cables Answer: B
Disponible en la aplicación Green Bridge
Descarga la aplicación Green Bridge CBT en tu teléfono u ordenador para acceder a las notas completas, preguntas de práctica y más.
Disponible en la aplicación Green Bridge
Descarga la aplicación Green Bridge CBT en tu teléfono u ordenador para acceder a las notas completas, preguntas de práctica y más.
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