3
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3.1.1. Unless the depth of the insert had been sufficient, it would not have been possible to make a large number of regrinds.
3.1.2. If a small torch bulb is joined to the terminals, the bulb will light up for a time, but soon it will become dim and go out.
3.1.3. If the core were solid it would form a closed path of very low reluctance.
3.1.4. Were the surface of the bearings harder and smoother the loss of the power would be less.
3.1.5. If a resistance is connected to the circuit the strength of current will decrease.
䳺 , . .
3.2.1. They (not to go) tomorrow if it rains.
3.2.2. I should be disappointed if you (not to come).
3.2.3. I (to drive) to the country if the weather were fine.
3.2.4. If I had known that it was going to rain, I (to take) an umbrella.
3.2.5. Unless we (to buy) tickets today, there will be no spare ones tomorrow.
, 䳺 (The Absolute Participle Complex).
3.3.1. Steel being one of the strongest metals, we use it for products where great strength is required.
3.3.2. The time of the beam`s travel and the velocity being known, the scientists were able to calculate the distance to different parts of the Moon`s surface with great precision.
3.3.3. This cycle is continued in each of the cylinders of the engine, the working strokes being so arranged that the crankshaft turns evenly.
3.3.4. It has two limitations, one being the small combustion space, the other being the limited total area of heating surface.
3.3.5. We have many polymers, new methods of their applying being worked out gradually.
, , 䳺 (The Absolute Participle Complex).
3.4.1. , .
3.4.2. , .
3.4.3. , .
, ᒺ (Complex Object).
3.5.1. Did you feel the bridge shake?
3.5.2. The handle is expected to be turned c.c.w. and raised to enable the cutter to be turned around.
3.5.3. We consider ourselves to have the right to claim an allowance of 10 %.
3.5.4. Put on a thicker uniform, I don`t want you to catch a cold.
3.5.5. I heard the door open and somebody enter the shop.
, ᒺ (Complex Subject). .
3.6.1. The rest of the goods are likely to be shipped in the first half of September.
3.6.2. This invention is considered of great importance
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3.6.3. The acceleration is assumed to be negative when the braking force slows down the motion.
3.6.4. The secondary circuits are reported by the operator to have been arranged incorrectly.
3.6.5. The fracture seemed to be caused by a heavy blow.
, ᒺ (Complex Object) ᒺ (Complex Subject).
3.7.1. , .
3.7.2. , .
3.7.3. ͳ , .
3.7.4. .
3.7.5. , .
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Transformers
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductorsthe transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core, and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.
If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding is in proportion to the primary voltage, and is given by the ratio of the number of turns in the secondary to the number of turns in the primary.
In the vast majority of transformers, the windings are coils wound around a ferromagnetic core, air-core transformers being a notable exception.
Transformers range in size from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of power grids. All operate with the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household ("mains") voltage.
The ideal transformer model assumes that all flux generated by the primary winding links all the turns of every winding, including itself. In practice, some flux traverses paths that take it outside the windings. Leakage results in energy being alternately stored in and discharged from the magnetic fields with each cycle of the power supply. It is not directly a power loss, but results in inferior voltage regulation, causing the secondary voltage to fail to be directly proportional to the primary, particularly under heavy load. However, in some applications, leakage can be a desirable property, and long magnetic paths, air gaps, or magnetic bypass shunts may be deliberately introduced to a transformer's design to limit the short-circuit current it will supply. Air gaps are also used to keep a transformer from saturating, especially audio-frequency transformers in circuits that have a direct current flowing through the windings.
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1. What is mutual induction?
2. How do transformers range in size?
3. Why does a leakage result?
4. Where are the transformers applied?
5. Where can leakage be a desirable property?
