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If more heat is generated by the resistor than can be dissipated, the resistor will overheat and become damaged. Resistor power rating is specified in watts. When calculating the power in resistors or resistances, the main equation to use whenever there is current flowing in 2 the resistance is I R. The physical size of a resistor is no indication of its resistance as a small resistor can have a very low or a very high resistance value.

A resistors physical size, however, does give some indication of its power rating. Whenever current flows Generally speaking the larger their physical size the higher its wattage rating. When resistors with electrical power in Watts higher wattage ratings are required, wirewound resistors fitted to metal heatsinks are generally used to dissipate the excessive heat. When selecting the appropriate resistor for a circuit, always try to select a resistor with a higher wattage rating than the actual calculated power dissipation for safety reasons as resistors that conduct lots of current can become very hot.

These coloured painted bands produce a system of identification generally known as a Resistors Colour Code. These coloured bands are usually printed towards one end of the resistors body to indicate the first digit with the colours being read from left to right. In the four-band system, the first band closest to the edge represents the first digit of the resistance value, the second band is the second digit, the third band is the decimal multiplier, which tells us how many zeros to add after the first two digits and the fourth band is the tolerance giving Digit, Digit, Multiplier, Tolerance.

The five-band system displays the coloured bands the same as for the four-band, except for an additional third coloured band to represent a third significant digit giving, Digit, Digit, Digit, Multiplier, Tolerance. The five-band system is used for high precision resistors with low tolerance.

These resistive networks have an equivalent resistance which is a combination of the individual resistors. It makes no matter what the combination or complexity of the resistor network is, all resistors obey the same basic rules defined by Ohm's Law above. Since all the current flowing through the first resistor has no other way to go it must also pass through the second resistor and the third and so on. Resistors in series have a Common Current flowing through them as the current that flows through one resistor must also flow through the others as it can only take one path.

Unlike the previous series circuit, in a parallel resistor network the current can take more than one path. Since there are multiple paths for the supply current to flow through, the current is not the same at all points in a parallel circuit. However, the voltage drop across all of the resistors in a parallel resistive network is the same. Then, Resistors in Parallel have a Common Voltage across them and this is true for all parallel connected elements.

This method of calculation can be used for calculating any number of individual resistances connected together within a single parallel network. If however, there are only two individual resistors in parallel then a much simpler and quicker formula can be used to find the total resistance value, and this is given as: 2.

The capacitor is a component which has the ability or "capacity" to store energy in the form of an electrical charge producing a potential difference across its plates. Capacitors consists of two or more parallel conductive metal or foil plates which are not connected or touching each other, but are electrically separated either by air or by some form of insulating material such as paper, mica, ceramic or plastic and which is commonly called the capacitors Dielectric.

When a sufficient amount of charge, Q measured in units of coulombs have been transferred from the source voltage to the capacitors plates, the voltage across the plates, Vc will be equal to the source voltage, Vs and the flow of electrons will cease. The voltage developed across the capacitors plates is not instantaneous but The material used to builds up slowly at a rate that depends on the capacitance value of the plates, separates the plates of a the greater the capacitance, the slower the rate of change of voltage in the capacitor from each other plates.

A capacitance of one farad, F, represents a charging current of one ampere when there is a voltage, V increase or decrease at a rate of of one volt per second. Capacitance, C is always positive and has no negative units. However, the Farad is a very large unit of measurement to use on its own so sub-multiples of the Farad are generally used such as micro-farads, nano-farads and pico-farads, for example. Also like resistors, there are also variable types of capacitors which allow us to vary their capacitance value for use in radio or "frequency tuning" type circuits.

The various types of capacitors include, disc and tubular ceramics made from aluminium oxide or titanium oxide, silvered mica, metallised film made using strips of waxed or oiled paper and aluminium foil, or with plastic dielectrics such as polyethylene, mylar, polypropylene, polycarbonate, and polyester, and finally large electrolytic capacitors in the form of Aluminum Electrolytic Capacitors and Tantalum Electrolytic Capacitors either polarised or non-polarised.

Variable capacitors change value due to the variation in the overlapping area of the plates, or by varying the spacing between parallel plates.

Air dielectric is used for the larger capacitance values. Trimmers and smaller variable types use very thin mica or plastic sheets as the dielectric between the plates. Placing capacitors in series effectively increases the thickness of the dielectric, decreases the total capacitance. The total capacitance of capacitors in series is calculated like the total resistance of parallel resistors. Connecting capacitors together in parallel effectively increases the area of the plates making the total capacitance equal to the sum of the individual capacitances like the total resistance of series resistors.

Capacitors in parallel all charge to the same voltage. The voltage, Vs connected across all the capacitors that are connected in parallel is the same.

Then, Capacitors in Parallel have a common voltage supply across them. Then, Capacitors in Series all have the same current so each capacitor stores the same amount of charge regardless of its capacitance. Capacitors connected together in series all have the same amount of charge. The direction of this magnetic field can be thought in terms of a wood screw being screwed into the conductor in the direction of the flow of current, with the head of the wood screw being rotated in the direction of the lines of force.

If we now take this length of wire and form it into a coil of N turns, the magnetic flux surrounding the coil is increased many times over for a given coil of wire compared with the flux produced by a single straight length. Also, if the current which is flowing through the coils conductor is increased in magnitude, the magnetic flux produced around the coil will also increase in value. However, as the strength of the magnetic flux increases, it induces a secondary An Inductor is a coil of voltage within the coil called a back emf electro-motive force.

Then for a coil of wire which opposes the wire, a self-induced voltage is developed across the coil due to the change in flow of current through current flowing through the coil. The polarity of this self-induced voltage produces itself in the form of a a secondary current in the coil that generates another magnetic flux which magnetic field opposes any changes to the original flux.

In other words, the instant the main current begins to increase or decrease in value, there will be an opposing effect trying to limit this change. But because the coil of wire is extremely long, the current through the coil cannot change instantaneously it takes a while for the current to change due mainly to the resistance of the wire and the self-induced effects of the wire coil. The ability of a coil to oppose any change in current is a result of the self-inductance, L of the coil.

This self- inductance, simply called inductance, value of an inductor is measured in Henries, H. Then the greater the inductance value of the coil, the slower is the rate of change of current for a given source voltage.

Then Inductance is the characteristic of an electrical conductor that opposes a change in current flow. An inductor is a device that stores energy within itself in the form of a magnetic field.

This results in a much stronger magnetic field than one that would be produced by a simple coil of wire. Inductors can also be fixed or variable. Inductors are mainly designed to introduce specific amounts of inductance into a circuit. They are formed with wire tightly wrapped around a solid central core which can be either a straight cylindrical rod or a continuous loop or ring to concentrate their magnetic flux.

The inductance of a coil varies directly with the magnetic properties of the central core. Ferrite and powdered iron materials are mainly used for the core to increase the inductance by increasing the flux linking the coil. Increasing levels of inductance can be obtained by connecting the inductors in series, while decreasing levels can be obtained by connecting inductors in parallel. However, there are certain rules for connecting inductors in series or parallel and these are based on the fact that no mutual inductance or magnetic coupling exists between the individual inductors.

In the Resistors in Series tutorial we saw that the different values of the resistances connected together in series just "add" together and this is also true of inductance. Inductors in series are simply "added together" because the number of coil turns is effectively increased, with the total circuit inductance LT being equal to the sum of all the individual inductances added together. The voltage drop across all of the inductors in parallel will be the same.

If the voltage across a resistor varies sinusoidally with respect to time, as it does in an AC circuit, the current flowing through the resistor will also vary. In an AC resistance, the current and voltage are both "in-phase" as there is no phase difference between them.

A circuit consisting of reactance inductive or capacitive resistance and a resistance will have an equivalent AC resistance known as Impedance, Z. Impedance is the phasor sum of the circuit's reactance, X and the resistance, R.

Note that although impedance represents the ratio of two phasors, it is not a phasor itself, because it does not correspond to a sinusoidal varying quantity. Impedance, which is given the letter Z, in a pure ohmic resistance is a complex number consisting only of a real part being the actual AC resistance value, R and a zero imaginary part, j0. Because of this Ohm's Law can be used in circuits containing an AC resistance to calculate these voltages and currents. As a pure resistor has no reactance, resistance is, for all practical purposes, unaffected by the frequency of the applied sinusoidal voltage or current.

In such circuits we can use both Ohms Law and Kirchoff's laws as well as simple circuit rules for calculating the voltage, current, impedance and power as we would in DC circuit analysis. When working with such rules it is usual to use rms values only. Capacitors oppose these changes in sinusoidal voltage with the flow of electrons through the capacitor being directly proportional to the rate of voltage change across its plates as the capacitor charges and discharges.

Unlike a resistor were the opposition to current flow is its actual resistance, the opposition to current flow in a capacitor is called Reactance. Like resistance, reactance is measured in Ohm's but is given the symbol "X" to distinguish it from a purely resistive ohmic R value and as the component in question is a capacitor, the reactance of a capacitor is called Capacitive Reactance, XC which is also measured in Ohms.

In a pure AC Capacitance circuit, the voltage and current are both "out-of-phase" with the current leading the o o o 5. The effect of a sinusoidal supply produces a phase difference between the voltage and the current waveforms.

In an AC circuit, the opposition to current flow through an inductors coil windings not only depends upon the inductance of the coil but also the frequency of the AC waveform. The opposition to current flowing through a coil in an AC circuit is determined by the AC resistance, more commonly known as Impedance Z , of the circuit. As the component we are interested in is an inductor, the reactance of an For more information visit our website at: www.

In other words, an inductors electrical resistance when used in an AC circuit is called Inductive Reactance. Inductive Reactance which is given the symbol XL, and is the property in an AC circuit which opposes the change in the current. Hack 7: Keyboard Props Binder clips can make your workplace more efficient and comfortable, too.

Some computer keyboards have tiny legs that prop them at a comfy angle for easy typing—however, if yours does not, simply remove the metal crooks from a binder clip and use them as makeshift props. Hack 8: Keep Cords and Wires in Shape Thanks to gravity and lots of use, electrical cords tend to fray and break off around their plug ends. Anyone with a Mac-brand laptop has experience with frayed charger wires. Not only is this irritating, but the exposed wiring can be dangerous.

For everyday tips and lifehacks, tune in to the Who Knew podcast on iTunes and Stitcher! And don't forget to follow us on Facebook and Twitter. After saving thousands per year using everyday tips and simple lifehacks, they started their own business in the hopes of sharing their knowledge with others.

They have been known to go into their friends' refrigerators to turn their eggs upside down so that they last longer. Jump to Navigation. April 26, About the Author. Bruce Lubin and Jeanne Bossolina-Lubin are the proud parents of three boys and more than a dozen books. Because of their temporary nature, they allow you to create circuits without soldering.

The holes in a breadboard are connected in rows both horizontally and vertically as shown below. Check out this post for more info on how to use a multimeter. A battery holder is a plastic case that holds batteries from 9V to AA. Test leads are great for connecting components together to test a circuit without the need for soldering. The advantage of these over normal screwdrivers is the precision tips of each driver.

These are very handy when working with electronics that contain tiny screws. When working with electronics, it seems you never have enough hands to hold everything. This is where the helping hand 3rd hand comes in.

Great for holding circuit boards or wire when soldering or tinning. A heat gun is used to shrink plastic tubing known as heat shrink to help protect exposed wire. Heat shrink has been called the duct tape of electronics and comes in handy in a wide variety of applications. These wires are used with breadboard and development boards and are generally AWG solid core wire. Jumper wires can have male or female ends depending on how they need to be used.

To do this, a soldering iron is the tool you would use. You can choose leaded or lead-free solder in a few diameters. Now its time to talk about the different components that make your electronic projects come to life. Below is a quick breakdown of the most common components and functions they perform. Switches can come in many forms such as pushbutton, rocker, momentary and others.

Their basic function is to interrupt electric current by turning a circuit on or off. Resistors are used to resist the flow of current or to control the voltage in a circuit.

The amount of resistance that a resistor offers is measured in Ohms. A variable resistor is also known as a potentiometer. These components can be found in devices such as a light dimmer or volume control for a radio. When you turn the shaft of a potentiometer the resistance changes in the circuit. A light-dependent resistor is also a variable resistor but is controlled by the light versus turning a knob. The resistance in the circuit changes with the intensity of the light.

These are often found in exterior lights that automatically turn on at dusk and off at dawn. Capacitors store electricity and then discharges it back into the circuit when there is a drop in voltage.

A capacitor is like a rechargeable battery and can be charged and then discharged. A diode allows electricity to flow in one direction and blocks it from flowing the opposite way. A light-emitting diode is like a standard diode in the fact that electrical current only flows in one direction. The main difference is an LED will emit light when electricity flows through it.

Inside an LED there is an anode and cathode. The longer leg of the LED is the positive anode side. Transistor are tiny switches that turn a current on or off when triggered by an electric signal. In addition to being a switch, it can also be used to amplify electronic signals. A transistor is similar to a relay except with no moving parts. A relay is an electrically operated switch that opens or closes when power is applied.