Introduction%20to%20Engineering%20Electrical%20Circuits%20and%20Controls%20-%201

1
Introduction to EngineeringElectrical Circuits
and Controls - 1

• Agenda
• Introduction to electrical circuits, controls and
  preparing simple electrical drawings.

2
Agenda

• Discuss basic concepts for electrical circuits
  and controls.
• Learn how to read and create simple electrical
  drawings.

3
Electrical Drawings

• Electrical drawings provide a complete
  description of the electrical circuitry for a
  product.
• The purpose of a circuit diagram is to clearly
  show how components are connected electrically.
  This is not the same as showing where components
  are physically, or how they have been laid out on
  a circuit board.
• Standard symbols are used.

4
Symbols for Basic Components in a Circuit
resistor
inductor
capacitor
voltage source
current source
switch
5
Example Single Use Camera Flash Circuit
6
Creating Electrical Circuit Diagram for a Device
- Flashlight
(Switch) S
(Resistive Load) R
(Battery) V
(Current) I
actual object
electrical drawing
Electrons flow from (-) to () by convention,
current is said to flow in the opposite direction.
7
Ohms Law
V IR
The voltage change V (volts) across any resistive
load is equal to the product of the current I
(amps) and the resistance R (Ohms).
8
Basic Relationship Power Law
P IV
Power dissipated P (watts) is equal to product of
the current I (amps) and voltage V (volts)
9
Example 1 Instructor Example
R 12 ohms
120 V
i ?
Current I V/R 120 V/12 Ohms 10 amps
Power P V I 120 V 10 Amps 1200 Watts
10
Example 2 Student Example
R 24 Ohms
240 V
I ?
I
P
11
Example 3 Resistance of Light Bulbs

• Without doing any calculations, which light bulb
  has the lowest resistance?
• 75 W bulb at 120 V
• 150 W bulb at 120 V

12
Example 3 Resistance of Light Bulbs, calculate
and compare

• Calculate the resistance using Power Law and Ohms
  Law. Use
• I P / V (P VI) R V / I
• Some groups do 75 W bulb
• Other groups do 150 W bulb
• Compare Results

13
Assignment 28

• Do problem set 1 on electrical circuits found in
  the assignment packet.