Electric Devices And Meters example essay topic

Experiment #7"Electric Devices and Meters " Physics - PHA 202 - PT 2 E Santos, Nickerson Jeff F. February 27, 20020001864 Experiment No. 7 Electric Devices And Meters OBJECTIVE: To familiarize the students with the different types of electric devices and meters. FOREWORD: In order to perform experiments dealing with electric circuits, you must become familiar first with the devices and meters needed for such experiment. Some of the most common devices and meters to be used is described below. 1) RESISTORS - Resistors are devices used to give a desired value of resistance.

They are inserted into a circuit in order to lower the current of to produce a desired voltage drop. There are two kinds of resistors: a) the Fix Resistor and, b) the Variable Resistor. The fix resistor has a specific value of resistance which cannot be changed, while the variable resistor may have a any value of resistance within a specified range. Resistors have two important characteristics: a) its resistance in Ohms and, b) its wattage rating.

Resistors are available in a wide variety of resistance values ranging from less than 1 ohm to mega ohms (M ). The power rating may be as high as 100 watts or may be lower than 1 watt. High-wattage resistors are usually of the wire wound type while low-wattage resistors are the carbon-composition type. The latter type is the one that we ordinarily see in which the resistance value is indicated by color codes. It is a fix resistor. For the variable resistor, it may be the plug type, the dial type or the switch type.

2) POTENTIOMETER - This is a variable resistor with three terminals. The two end terminals gives its fix maximum resistance while the middle terminal and an end terminal makes it a variable resistor. 3) RHEOSTAT - This is a two terminal variable resistor that is used to vary the current in the circuit. Generally, rheostats are high-wattage wire wound resistors. 4) SWITCHES - Switches are devices used to make or break circuits. They are classified by the number of poles and the number of throws.

For example, the single-pole single-throw (SPST) switch with only one pole and can be thrown only in one position. 5) BATTERY / DRY CELL - Batteries serves as a source of electricity of the direct current (DC) type. It is usually made up of cells connected in series to give a desired value of voltage. It has two terminals, a positive and a negative terminal. 6) TRANSFORMER - A transformer is an electrical device capable of changing a voltage at one level to another whether higher or lower.

It is commonly used to transform a 220 volts AC to 6 and 12 volts AC. 7) VARIABLE AUTOTRANSFORMER (VARIAC) - This is a special type of transformer capable of changing a voltage at one level to another level which may be varied from a specified minimum value to a specified maximum value. For example, the input voltage is 220 volts, the output voltage may range from 0 to 220 volts. This device is very important in situations where different values of voltage is needed.

8) RECTIFIER - This is an electronic device used to change AC voltage to DC voltage through the action of diodes. A varia c-rectifier combination is capable of giving a variable DC output. 9) AMMETERS - These are metering devices for the measurement of electric current. It may be of the DC or AC type. Furthermore, the term ammeter refers to meters capable of measuring current in amperes. For low values of current, there are the milli ammeter and the micro ammeter.

10) VOLTMETERS - These are metering devices for the measurement of voltages. Like ammeters, it may be of the DC or the AC type. 11) OHMMETER - This is an instrument for the measurement of electric resistance. This function is usually part of a multimeter arrangement like the VOM which will be discussed next.

12) VOLT-OHM-MILLIAMMETER (VOM) - This is a popular instrument, properly known as "the tester". As its name suggests, it can be used for measuring voltages (either AC or DC), for measuring resistances (as an ohmmeter) or for measuring DC currents in milliamperes (DC milli ammeter). The VOM is provided with a function switch which is used when shifting from one function to another. 13) GALVANOMETER - This is an instrument used for measuring or detecting very small amount of currents. It can also be used as an ohmmeter, an ammeter and a voltmeter depending on the type of resistor to be connected to it. 14) CAPACITORS -Capacitors are devices capable of storing electric charges.

When a capacitor is charged, it can be think of as a voltage source. It's ability to store electric charges is measured by its capacitance. The basic unit of capacitance is the Farad (F). But one Farad is a very large value. For this reason, the typical unit of capacitance is expressed in microfarad (μ F)... CONNECTING AMMETERS AND VOLTMETERS The general rule for connecting ammeters and voltmeters is "Ammeters are connected in series while Voltmeters are connected in parallel".

For the DC type, polarity markings must be considered, otherwise the meter will read downscale. For the AC type, there is not much of a problem. However, proper caution must be observed when using both types of meters. The figure below illustrates the proper way of connecting an ammeter and a voltmeter. Ammeter connected in series LV RV Source Load RX Voltmeter connected in parallel Fig 2-1 Proper way of connecting an ammeter and a voltmeter.

SCHEMATIC SYMBOLS OF ELECTRIC DEVICES AND METERS When drawing electric or electronic circuits, devices and meters are not drawn as they appear to the eye. Instead symbols are used to represent them. Shown below are the schematic symbols of common electric devices and meters. Device / Meter Symbol Device / Meter Symbol Fix Resistor Voltmeter Rheostat Ammeter Potentiometer Ohmmeter SPST Switch Galvanometer Battery / Dry cell Milliammeter Fuse Capacitor Transformer Variable Auto Transformer APPARATUS: : Fix Resistor: Variable Resistor: Rheostat: DC Voltmeter: Switch: VOM: Battery / dry Cell: Galvanometer: Rectifier: Capacitor: DC Ammeter: Connecting wires PROCEDURE: PART 1 FAMILIARIZATION WITH METERS AND DEVICES Step 1: Identify all the devices and meters on hand. Step 2: Make a sketch of all the meters and devices giving emphasis on the most vital parts. Label all these parts.

Step 3: For all the devices and meters on hand, take note of the following and write it beside the respective sketches: a) For the resistance device, the resistance value (s) and the wattage (power) and / or ampere (current) rating. b) For the meters, the range (s) of values of voltage / current/ resistance that the meter is capable of measuring. c) For the transformers (including the Variac) and the rectifier, the voltage and current ratings. d) For the capacitor, its capacitance and its voltage rating. QUESTION: 1) Prior to this experiment, which among the devices and meters that you used are you already familiar of, and how come? - The devices that I am already familiar of are: The dry cell, transformer, and the switch. I am already familiar with these devices mainly because they are frequently used in our household and they are also commonly used by other people. 2) What is an ideal ammeter? Voltmeter?

- An Ideal Ammeter is an instrument used to measure the magnitude of an electric current of several amperes or more. While a Voltmeter is a device used to measure the differences of electric potential present in the electric current. 3) How can a galvanometer function as an ammeter? A voltmeter?

An ohmmeter? Draw the circuit diagram. - A galvanometer can also function as an ammeter, a voltmeter, and an ohmmeter. It all depends on the resistors that we connect to it. To be able to use a galvanometer as a voltmeter, we simply connect a galvanometer in a series connection together with a high capacity resistor. And to use it as a ammeter, we simply connect a galvanometer and place a bypass or shunt to prevent the high wattage of the current to flow to the galvanometer.

4) Cite other uses of the VOM aside from measuring voltages, currents and resistances. - The VOM, also know as the Volt-Ohm-Milliammeter, can be used as a "tester". It can tell if an electrical device is working properly by testing if there is still an electric current running through its system. That way the electrician can identify the damage on the device. (if there is any) ANALYSIS: Based on the experiment, I observed that most of the devices we used are already familiar to me.

Such as the dry cell, switch and the transformer. These devices are commonly used and it is commercially distributed so that's why I am already familiar with it. Another thing I noticed is that the Ammeter, Voltmeter, and Galvanometer have the same shape but they differ in their terminals and scales. Also, the devices that we borrowed are somewhat old and are labeled "broken". But its fine because I'm not going to use it, I just want to see it to be able to draw it. CONCLUSION: In the study of electricity, we need to familiarize ourselves on the different electric devices and meters, as well as there uses and corresponding scales.

Resistors offer opposition to an electric current, while Rheostats are used for such purposes as controlling the speed of electric motors and dimming electric lights. Switches turn the electric current on and off, and a dry cell is a device that converts chemical energy into electrical energy and serves as an electrical source. A Rectifier is a component of an electric circuit that is used to change an alternating current to a direct current. For measuring electrical dimensions, an electric meter is used. An Ammeter is an instrument used to measure the magnitude of an electric current of several amperes or more, while a Voltmeter is an instrument used to measure differences of electric potential. And a Galvanometer is an instrument used to determine the presence, direction, and strength of an electric current in a conductor.

A galvanometer can be a voltmeter, ammeter and a n ohmmeter depending on the type of resistor that is connected to it. A Capacitor or Condenser, device for the storage of electric charge. Simple capacitors consist of two plates made of an electrically conducting material and separated by a non-conducting material or dielectric. It is used on electric currents to facilitate the flow of electric charge. A Transformer is a device that is used in common household appliances. It is a voltage converter, it converts a higher voltage circuit to a lower voltage circuit and vice versa, the one commonly used converts a 220-volt circuit to a 110-volt circuit.

It is very useful for low voltage appliances. Another electric device not mentioned in the manual is the AVR or Automatic Voltage Regulator, as it name suggests, it regulates the flow of electric charge on a circuit so that it can flow in a uniform magnitude. It is commonly used on electric-sensitive devices such as personal computers and the like.