Introduction of Electrical Engineering

Resistance
• It is opposition to flow of current through a circuit, it depends how narrow is its cross section and how long its length. • In other words the electrical resistance of a conductor is directly proportional to its length and inversely proportional to its cross sectional area.

RESISTANCE
Resistance to the flow of the current. Measured in Ohms. Flow of current through a conductor is analogous according to flow of water in pipe if make path to water flow narrow so less water flow and vice versa

• Ohm’s Law explains the relationship between voltage (V or E), current (I) and resistance (R) .It states that potential difference between two ends of a conductor is directly proportional to current flowing through it, provides its temperature and other physical parameters remains unchanged

• 1. Assuming the resistance does not change: As voltage increases, current increases. as voltage decreases, current decreases. • • • 2. Assuming the voltage does not change: As resistance increases, current decreases. As resistance decreases, current increases.

R=V I I= V R V (E) = I x R

OHM’S LAW

How do calculate?
Battery voltage is 12V Current is Amp ? Resistance 2 Ohm

OHM’S LAW IN GRAPICAL FORM

ENERGY
Work has to done in transferring a charge through an element. If the current is entering the positive terminal of an element, there must be some external force that is driving the current through element. This external force delivering energy and element absorbing energy. On the other hand if current is leaving the positive terminal the element is delivering energy to external circuit. The unit of energy is joule(J)

Unit of Energy In Electrical
• If a charge Q flows through element for time t, and if potential difference across elements is v , the energy delivered or work done is • Energy=Work=Voltage*charge =V*Q=pt=VIt • When 1 watt of power is delivered to an electrical load for 1 watt- second or 1 joule(J). • Watt-second is very small...