Dc circuit physics lab report

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Direct Current (DC) Circuits Introduction In this lab, we will get acquainted with various components of electrical circuits. We will learn: how to make simple circuits using a battery (or power supply), light bulbs, resistors; draw the circuit diagram; how to use color code to read the resistance of the resistor; how to use the measuring tools like a digital multimeter – DMM; how to connect the DMM to measure the resistance, voltage and current. We will learn how to simplify the circuit by replacing the circuit diagram with an equivalent one. Text reference: Young and Freedman §§ 26.1, 26.3. We will investigate the behavior of direct current (DC) electrical circuits. We will study the flow of electrical current in a circuit from the battery or power supply, through the wires, and through various combinations of light bulbs and/or resistors.

A simple electrical circuit usually has a power (energy) source such as a battery or power supply and resistors such as a light bulb or a carbon resistor. Here are the symbols for some electrical components you may see in circuit diagrams of the lab manuals of this lab course:

A closed circuit is a path along which current carriers (electrons in conductors) can flow. Current does not flow in an open circuit. A circuit in which there is a single pathway is known as a series circuit whereas a circuit that has multiple (more than one) possible paths is known as a parallel circuit. Resistors impede the flow of current in a circuit. We assume that connecting leads (conductors) have negligible resistance, while the insulators have very large resistance. Many resistors obey Ohm’s Law (V = IR), which states that the current I through a resistance R is proportional to the voltage V across the resistor. We will study Ohm’s law in the next lab class experiment. Part 1. Light Bulbs

1. Simple circuit Make a simple circuit using a battery or DC power supply, a light bulb (in its holder), and some of the connecting leads.

a) What happens to the light bulb when you close the circuit? ___________________________________________________________________

b) Draw a circuit diagram representing your circuit using the symbols from above: Try to remember how brightly the bulb is shining in step 1.

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2. Light bulbs in Series Now add a second identical bulb in series (you will need to disconnect your circuit first).

a) Draw a proper diagram representing your circuit. What do you observe about the light intensity (brightness) in each bulb compared to a single bulb in the previous step? __________________________________________________________________

b) What happens if you remove one of the light bulbs from its holder? _________________________________________________________________

3. Light bulbs in Parallel Disconnect the circuit from step 2 and add the second bulb in parallel to the first.

a) Draw a proper diagram representing your circuit. What do you observe about the light intensity in each bulb compared to a single bulb in step 1?

__________________________________________________________________ b) What happens if you remove one of the light bulbs from its holder? __________________________________________________________________

Part 2. Resistors

The Carbon Resistors A common type of resistor used in electrical circuits is made from a carbon composition in the form of a small solid cylinder with a wire lead attached to each end. The nominal resistance value is specified by a color code as it is shown for example in Figure 1.

Figure 1. Carbon resistor with 4 color band

The first three bands give the resistance in ohms in the form R = AB x 10C Ohms, where A, B, and C are integers between 0 and 9. The first band is A, the second B and the third C. The color code for the integer is:

black brown red or