Electric Circuit I Lab Manual. Session # 1

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1 Electric Circuit I Lab Manual Session # 1 Lab Policies 1. Each lab session lasts 90 min and starts promptly. A brief introduction with demo may be given by the instructor at the beginning of the lab. Everybody has to finish on time, so please time yourself carefully. 2. Preparing the lab is very important as it will save you time and allow you to work more efficiently. The pre-lab includes reading the lab manual in advance, and if necessary reviewing the material in the textbook. 3. Pre-lab Quiz in some random weeks there will be a short quiz at the first 5 minutes of the lab. The quiz mark is worth 20% of the overall lab mark. 4. Student partnership, each lab is done in groups of two. The team approach encourages interaction and helps with the debugging and data collection. Each student has his/her own lab notebook and is responsible for recording the pre-lab, recording the measurement data. Copying of data from other groups or altered information will result in a zero grade for the course. 5. Instruments and supplies the major instruments you will be available in the lab. A selection of wires, cables and connectors are inside your kit. Small parts (resistors, capacitors, transistors, ICs) will be available in the bins in the lab area. Capacitors, transistors and integrated circuits (ICs) can be reused and should be left on the table in the same manner as they were obtained. 6. Leave your workplace at least as clean and tidy as you found it. Put everything back in its proper place. 7. Grading Policy The laboratory work has a weight of 15% of the total grade of the course. The lab marks are divided as follows: 3 Marks for Pre-Quiz.

2 6 Marks for Lab work (Measurements and Simulations). 6 Marks for answering the questions & writing the end of lab report. 8. Precautions Electronic test equipment can be damaged if incorrectly used. The function generator will be damaged if a large DC or AC voltage is applied to the outputs. The oscilloscope also has input limitations. Power supplies can also be damaged if an external voltage in excess of the supply output voltage is fed back into the supply. The most common ways multi-meters are damaged are by trying to measure voltage when the meter is set to measure current or resistance or by exceeding the maximum voltage when in the voltage measurement mode. Think twice before connecting a meter. In particular, check the position of the function switch and ensure the test leads are connected to the proper inputs on the meter. If you make a mistake you could blow the meter s internal fuse or damage the converter chip. Our lab procedures are designed to avoid these problems but you should always be aware of your test equipment s limitations. 9. No foods or drinks are allowed inside the lab for any reason. 10. Report writing, at the end of each lab you have to hand in the lab report to your lab instructor.

3 Session (1): Electrical Quantities Objective: The objective of this experiment is to learn different electrical properties as Current, Voltage, Resistance and Power. Theory: 1. Current: (i or I) is the flow of electric charge from one point to another, and it is defined as the rate of movement of charge past a point along a conduction path through a circuit, or i = dq/dt. The unit for current is the ampere (A). One ampere = one coulomb per second. Note: To measure the current we use Ammeter.Some ammeters are fabricated and used to measure current only while others are fabricated in a multimeter to be used to measure other electrical parameters too. Ammeter must be connected in series to the resistance in which current is to be measured therefore it must be of very small resistance not to affect the current passing in this resistance i.e. R meter = zero but since there is no ideal case ever therefore the practical ammeter have a certain small resistance. 2. Voltage: (v or V) is the "potential difference" between two points, and it is defined as the work, or energy, required moving a charge of one coulomb from one point to another. The unit for voltage is the volt (V). One volt = one joule per coulomb.

4 Note: To measure the voltage we use voltmeter.some voltmeters are fabricated and used to measure voltage only while others are fabricated in a multimeter to be used to measure other electrical parameters too. Voltmeter must be connected in parallel to the resistance across which voltage is to be measured therefore it must be of very large resistance not to withdraw current from resistance and therefore not to affect its voltage. Ideally, voltmeter resistance R meter= infiniti but since there is no ideal case ever therefore the practical voltmeter have a certain large resistance. 3. Resistance: (R) is the "constant of proportionality" when the voltage across a circuit element is a linear function of the current through the circuit element, or V = IR. A circuit element which results in this linear response is called a resistor. The unit for resistance is the Ohm (O). One Ohm = one volt per ampere. The relationship V = IR is called Ohm's Law. Note: To measure the Resistance we use Ohmmeter.Some Ohmmeter are fabricated and used to measure resistance only while others are fabricated in a multimeter to be used to measure other electrical parameters too. To measure the resistance, the resistance must be disconnected from the circuit in which it lie in and then connected across the Ohmmeter to measure its resistance. Never measure the resistance when Power supply is ON. 4. Power: (p or P) is dissipated in a resistor in the form of heat. The amount of power is determined by: p=vi, p=i2r, or p=v2/r. The latter two equations are derived by using Ohm s Law (V = RI) and making substitutions into the first equation for power. The unit for power is the watt (W) One watt = one joule per second.

5 Note: To measure the Power we get voltage across the resistance and current passing through it then use the law to get value of DC power. Measuring Instruments The multimeter used in our lab is shown in the figure 1. It has two ranges for DC voltage measurements which are V (volts) and mv (mill volts). It can measure current by setting it to ma where the displayed measurement will be in ma and can measure resistance if it is set to O.

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7 Resistor Color Code Objective: The objective of this experiment is to allow you to read the color code of a resistor. Including the tolerance. Introduction: Depending on context, the color bands can represent digits, multipliers, accuracy tolerance, or temperature coefficients. How can the value of a resistor be worked out from the colors of the bands? Each color represents a number according to the following scheme: The first band on a resistor is interpreted as the FIRST DIGIT of the resistor value. For the resistor shown below, the first band is yellow, so the first digit is 4: The second band gives the SECOND DIGIT. This is a violet band, making the second digit 7. The third band is called the MULTIPLIER and is not interpreted in quite the same way. The multiplier tells you how many types of nougat you should write after the digits you already have. A red band tells you to add 2 nougats. The value of this resistor is therefore ohms, that is, 4 700, or 4.7. Work

8 through this example again to confirm that you understand how to apply the color code given by the first three bands. The remaining band is called the TOLERANCE band. This indicates the percentage accuracy of the resistor value. Most carbon film resistors have a gold-colored tolerance band, indicating that the actual resistance value is with + or - 5% of the nominal value. Other tolerance colors are: When you want to read off a resistor value, look for the tolerance band, usually gold, and hold the resistor with the tolerance band at its right hand end. Reading resistor values quickly and accurately isn't difficult, but it does take practice!

9 Example Resistor Color Codes