Introduction to DC circuits

1 / 24

# Introduction to DC circuits - PowerPoint PPT Presentation

Introduction to DC circuits . A brief overview on the basics. jbugni@nmu.edu. The Atom. Basic unit of matter Made up of tiny particles, two are important in electricity Protons Contained in the nucleus (center) of the atom Have a positive charge Electrons

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'Introduction to DC circuits' - chipo

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Introduction to DC circuits

A brief overview on the basics

jbugni@nmu.edu

The Atom
• Basic unit of matter
• Made up of tiny particles, two are important in electricity
• Protons
• Contained in the nucleus (center) of the atom
• Have a positive charge
• Electrons
• Move around the nucleus in paths called shells
• Have a negative charge
• Electrons in the outer most shell are called valence electrons
The Atom cont.
• Amount of negative charge of each electron is equal to the amount of positive charge of each proton
• If enough energy is applied to an atom, some valence electrons will leave the atom
• Ions
• Charge atom
• Negative ion has more electrons than protons
• Positive ion has more protons than electrons
• Ions with similar charges repel, different charges attract
• Current flows when electrons move from one atom to another
The Atom cont.

What is a circuit?
• Defined as a system of conductors and devices through which electrons can move.
• Consists of three characteristics
• Must contain a power source
• Complete path for current flow from one side of the power source to the other
• Contains some type of resistance to limit the amount of current.
Example of basic circuit

Switch

Light bulb

Conductor

Battery

Voltage
• Measured in volts
• Electrical pressure used to move electrons throughout the circuit
• Also defined as the potential difference between two unlike charges
• Think of voltage as the water pressure in a garden hose
Current
• Measured in amps or ampere
• Movement of electrons through the circuit
• Think of the water flow in the garden hose
• DC refers to direct current or movement of electrons in one direction
Resistance
• Measured in ohms
• Opposes the movement of current
• Reduces the amount of current in a circuit
• Think of kinking the garden hose
• May also be referred to the load of the circuit
Conductors
• A solid, liquid or gas which electrons can easily pass through
• Most commonly made from copper
Schematic Diagrams
• Standard way of communicating information in electricity and electronics
• Components are shown by graphic symbols
• May not accurately represent the actual location of components
Electrical Symbols

http://alldatapro.com/alldata/PRO~V156153136~C21290~R0~OD~N/0/41746505/42420070/42420075/42420077/34853741/34869956/34849309/144051240

Example of Schematic

http://alldatapro.com/alldata/PRO~V156153136~C21290~R0~OD~N/0/41746505/42420070/42420075/42420077/34853741/34869956/34869958/56473437

Ohm’s law
• Discovered by German physicist Georg Simon Ohm
• Shows the relationship of resistance (R), current (I) and voltage (E) along with power (W)
• The most common equation is E=IR, where voltage is equal to resistance times current
• Basis for all study of electrical properties

Ohm’s law

http://www.uakron.edu/groups/chemcar/docs/ohm.pdf

E=IR
• For example: If a circuit has a constant power source of 12 volts and 4 amps of current, the resistance of the circuit must be 3 ohms (Ω)
• 12=4×R therefore R=12÷4=3

http://alldatapro.com/alldata/PRO~V155748232~C35580~R0~OD~N/0/80851247/83211660/83214935/83214937/34853741/34869214/34869215/34869322/34869325/146660096

Series Circuit
• Only one path for current to flow
• Total resistance of circuit is the sum of all resistances
• Current is consistent throughout the circuit
• Voltage drop is amount of voltage required to force the current through the load or resistance
• Sum of all the voltage drops equals the total voltage applied to the circuit
Series Circuit Schematic

http://www.cybermike.net/reference/liec_book/DC/00090.jpg

Parallel Circuit
• Contain multiple connections or branches
• Total current is divided between the branches
• Determined by the resistance of the branch
• Calculated by Ohm’s law
• Voltage is the same on all the branches
• Total resistance decreases as more branches are added
• Always less than the branch with lowest resistance
Parallel Circuit cont.
• Resistance formulas
• Two resistances of unequal value
• RT=(R1 × R2)÷(R1 + R2)
• All resistances are equal in value
• RT = (value of one resistance) ÷ (number of resistances)
• If resistances are not all equal in value
• RT = 1 ÷ (1/R1 + 1/R2 + 1/R3 + … + 1/RN)
Parallel Circuit Schematic

http://www.faqs.org/docs/electric/DC/00083.png

Series-Parallel Circuit
• Combination of both series and parallel circuits
• Requires formulas from both series and parallel circuits to calculate resistance, current and voltage drops
• Most electrical devices have series-parallel circuits
Series-Parallel Schematic

http://www.faqs.org/docs/electric/DC/00123.png

Other sources
• Buban, P., Schmitt, M. L., & Carter Jr., C. G. (1992). Understanding Electricity and Electronics Technology. Peoria: Macmillan/McGraw-Hill.
• Grob, B. (1992). Grob Basic Electronics. Westerville: Macmillan/McGraw-Hill.