A transformer consists of two coils (often called 'windings') linked by an iron core. There is no electrical connection between the coils; instead they are linked by a magnetic field created in the core.
Transformer only works with AC (alternating current) because they require a changing magnetic field to be created in their core. Step-up transformers increase voltage, step-down transformers reduces voltage. Most power supplies use a step-down transformer to reduce the dangerously high mains voltage to a safer low voltage. The input coil is called the primary and the output coil is called the secondary.The two lines in the middle of the transformer symbol represent the core.
Transformers waste very little power so the power out is (almost) equal to the power in. Note that as voltage is stepped down current is tapped up. Alternating current flowing in the primary (input) coil creates a continually changing magnetic field in the iron core. This field also passes through the secondary (output) coil and the changing strength of the magnetic field induces an alternating voltage in the secondary coil.
If the secondary coil is connected to a load the induced voltage will make an induced current flow.The correct term for the induced voltage is 'induced electromotive force' which is usually abbreviated to induced e. M. F. The iron core is laminated to prevent 'eddy currents' flowing in the ore.
These are currents produced by the alternating magnetic field inducing a small voltage in the core, Just like that induced in the secondary coil. Eddy currents waste power by needlessly heating up the core but they are reduced to a negligible amount by 8 Hardware Portrayal laminating the iron because this increases the electrical resistance of the core without affecting its magnetic properties.The ratio of the number of turns on each coil, called the turns ratio, determines the ratio of the voltages. A step-down transformer has a large number of turns on its primary (input) oil which is connected to the high voltage mains supply, and a small number of turns on its secondary (output) coil to give a low output voltage.
Turns ratio = UP Np ? Vs. Ins and power out = power in Vs. x Is = UP x Ip UP = primary (input) voltage Np = number of turns on primary coil and Ip = primary (input) current Vs. = secondary (output) voltage Ins = number of turns on secondary coil Is ? secondary (output) current 3. DIODE Fig.
3. 3 Symbol of Diode Fig. 3. 4 Diode In electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. The term usually refers to a semiconductor diode, the most common type today. This is a crystalline piece of semiconductor material connected to two electrical terminals.
The most common function of a diode is to allow an electric current to pass in one direction (called the diode's forward direction) while blocking current in the opposite direction (the reverse direction).Thus, the diode can be thought of as an electronic version of a check valve. This unidirectional behavior is called rectification, and is used to convert alternating current to direct current, and to extract modulation from radio signals in radio receivers. Electricity uses up a little energy pushing its way through the diode, rather like a person pushing through a door with a spring. This meaner that there is a small voltage across a conducting diode, it is called the forward voltage drop and is about 0. IV for all normal diodes which are made from silicon.
The forward voltage drop of a diode is almost constant whatever the current passing through the diode so they have a very steep characteristic. 9 Hardware Portrayal When a reverse voltage is applied a perfect diode does not conduct, but all real diodes leak a very tiny current of a few PA or less. This can be moored in most circuits because it will be very much smaller than the current flowing in the forward direction. However, all diodes have a maximum reverse voltage (usually IV or more) and if this is exceeded the diode will fail and pass a large current in the reverse direction, this is called breakdown.
. 3 CAPACITOR Fig. 3. 5 Symbol of Capacitor Fig. 3.
6 Capacitor A capacitor or condenser is a passive electronic component consisting of a pair of conductors separated by a dielectric. When a voltage potential difference exists between the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the plates. The effect is greatest between wide, flat, parallel, narrowly separated conductors. An ideal capacitor is characterized by a single constant value, capacitance, which is measured in farads.This is the ratio of the electric charge on each conductor to the potential difference between them.
In practice, the dielectric between the plates passes a small amount of leakage current. The conductors and leads introduce an equivalent series resistance and the dielectric has an electric field strength limit resulting in a breakdown voltage. 3. .
1 . ELECTROLYTE CAPACITOR Electrolytic capacitors are pollarded and they must be connected the correct way round - at least one of their leads will be marked + or They are not damaged by heat when soldering.There are two designs of electrolytic capacitors; axial where the leads are attached to each end and radial where both leads are at the same end. Radial capacitors tend to be a little smaller and they stand upright on the circuit board. It is easy to find the value of electrolytic capacitors because they are clearly printed with their capacitance and voltage rating.
The voltage rating can be quite low ND it should always be checked when selecting an electrolytic capacitor. If the circuit parts list does not specify a voltage, choose a capacitor with a rating which is greater than the circuit's power supply voltage. IV is a sensible minimum for most circuits. 10 Hardware Portrayal
