1. Circuit Analysis I

2. Recap Active and Passive electronic components
Current: Flow of charges
Voltage: Work done per unit charge
Ampere and Volt
Unit Prefixes: milli, micro, Mega, Kilo etc
Scientific notation: 3.1 x 106

3. Today’s Menu Resistance Types of resistors Voltage sources
Current sources
Basic electrical circuit
Ohm’s Law
Simple calculations using Ohm’s Law

4. Resistance
Resistance is the opposition to current i.e. hindrance in the path of current
One ohm (1 Ω) is the resistance if one ampere (1 A) current flows in a material when one volt (1 V) is applied across it.
Conductance is the reciprocal of resistance:
SI Unit of coComponents designed to have a specific amount of resistance are called resistors.
nductance is Siemens (mho).
Symbols for resistors

5. Types of Resistors
There are four main types of resistors on the basis of material and construction:
Carbon Composition Resistor - Made of carbon dust or graphite paste, low wattage values
Film or Cermet Resistor - Made from conductive metal oxide paste, very low wattage values
Wire-wound Resistor - Metallic bodies for heatsink mounting, very high wattage ratings and high precision
Semiconductor Resistor - High frequency/precision surface mount thin film technology

6. Types of Resistors
On the basis of resistance value there are two types:
Fixed resistors and variable resistors
Variable resistors include the potentiometer and rheostat. A potentiometer can be connected as a rheostat.
The center terminal is connected to the wiper

7. Resistor color coding

8. Test yourself
What is the resistance and tolerance of each of the four-band resistors?
5.1 kW ± 5%
820 kW ± 5%
47 W ± 10%
1.0 W ± 5%

9. Electromotive force
Voltage generated by a battery is termed as its electromotive force (measured in volts not Newtons)
A source of emf can be thought of as a kind of charge pump that acts to move positive charge from a point of low potential through its interior to a point of high potential by chemical, mechanical or other means.
In circuit theory two types of sources exist:
1. Current Sources
2. Voltage Sources

10. Ideal Voltage Source
Voltage across it is independent of the current through it.
Ideal voltage source has no internal resistance
Real voltage sources do have a finite internal resistance

11. Ideal Current Source
Current does not depend upon any voltage(s).

12. Electric Circuit
An interconnection of electronic components designed to produce a desired result. A basic circuit consists of a source, a load, and an interconnecting path.

13. Ohm’s Law
Current established is directly proportional to the voltage applied in a circuit.
Formula for voltage,
V=IR
V=voltage
I=current
R=resistance

14. Formula for current:
I=V/R
Formula for resistance:
R=V/I

15. Calculate current when resistance and voltage are known:
Example:
V=100 V, R=22 Ω, I=?
I = V / R = 100 / 22 = 4.55 A
There are 4.55 A in this ciruit.

16. If the resistance is changed to 47 ohm and voltage to 50V, what is the new value of current?
I = V / R = 50 / 47 = 1.06 A

17. When voltage is 50V and resistance is 1.0kΩ, find the value of current?
Remember 1.0kΩ is equal to 1 x 103 Ω , so current will be
I = 50 V / 1.0 kΩ = 50 V / 1 x 103 Ω = 50 x 10-3 A

18. V=30V, R=5.6kΩ
I = 30 / 5.6kΩ = 5.36mA