Unit 2 Electrical Quantities and Ohm’s Law · Electrical Quantities and Ohm’s Law A complete...

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Transcript of Unit 2 Electrical Quantities and Ohm’s Law · Electrical Quantities and Ohm’s Law A complete...

Unit 2

Electrical Quantities and Ohm’s Law

A coulomb is a quantity measurement for

electrons.

One coulomb contains 6.25 x 1018

electrons, or 6,250,000,000,000,000,000

electrons.

Unit 2

Electrical Quantities and Ohm’s Law

The ampere is a measurement of the amount of

electricity that is flowing through a circuit.

One ampere (A) is defined as one coulomb of

electricity flowing past a given point in one

second.

Unit 2

Electrical Quantities and Ohm’s Law

Compare and contrast these two systems.

Unit 2

Electrical Quantities and Ohm’s Law

There are two theories about current flow.

Electron flow theory describes current flow from

negative to positive.

Conventional current flow theory states

electrical current flows from positive to

negative.

Unit 2

Electrical Quantities and Ohm’s Law

Conventional current flow theory and electron flow theory.

Unit 2

Electrical Quantities and Ohm’s Law

Electrons moving from atom to atom.

Unit 2

Electrical Quantities and Ohm’s Law

Electrical sources are divided into two basic

types:

– Direct Current (DC) which is unidirectional

(one way).

– Alternating Current (AC) which is

bidirectional (two way, or back and forth).

Unit 2

Electrical Quantities and Ohm’s Law

A complete path must exist before electricity can

flow through a circuit.

A circuit with a complete path for electrical flow is

called a closed circuit.

If the circuit path is incomplete or broken, this is

called an open circuit.

Unit 2

Electrical Quantities and Ohm’s Law

A simple switch

closes and

opens an

electrical

circuit.

Unit 2

Electrical Quantities and Ohm’s Law

A short circuit has an unintended shorter pathway.

Unit 2

Electrical Quantities and Ohm’s Law

The basic principle of the instantaneous effect of

electric impulses.

Unit 2

Electrical Quantities and Ohm’s Law

The impulse of electricity can travel faster than light. It would take light 1.3 seconds to travel around the earth 10 times. If a wire were wrapped around the earth 10 times, when the switch was closed the light would come on almost instantly.

Unit 2

Electrical Quantities and Ohm’s Law

A volt or voltage is electrical pressure.

Unit 2

Electrical Quantities and Ohm’s Law

An ohm is the unit of resistance or opposition to the flow of

electricity.

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Electrical Quantities and Ohm’s Law

The watt is the unit of electrical power.

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Electrical Quantities and Ohm’s Law

Force equals flow rate times pressure.

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Electrical Quantities and Ohm’s Law

Amperes times volts equals watts.

Unit 2

Electrical Quantities and Ohm’s Law

Common power units.

Unit 2

Electrical Quantities and Ohm’s Law

Ohm’s law states that in a DC (Direct

Current) circuit, the current is directly

proportional to the voltage and inversely

proportional to the resistance.

E (volts) = I (amps) x R (ohms)

Unit 2

Electrical Quantities and Ohm’s Law

Ohm’s Law Symbols:

P is the symbol for Watts.

E is the symbol for Volts.

I is the symbol for Amperes.

R is the symbol for Resistance or Ohms.

Unit 2

Electrical Quantities and Ohm’s Law

Ohm’s Law states that it takes one volt to push

one ampere through one ohm.

E = Volts

I = Amps

E = I x R

I = E / R

R = E / I

R = Resistance

Unit 2

Electrical Quantities and Ohm’s Law

Using the Ohm’s law chart.

E = I x R I = E / R R = E / I

Unit 2

Electrical Quantities and Ohm’s Law

Adding P (watts) to the Ohm’s law chart.

P = E2 / R

P = E x I

P = I2 x R

R = E / I

R = P / I2

R = E2 / P

I =

I = P / E

I = E / R

E =

E = I x R

E = P / I

RP

PR

Unit 2

Electrical Quantities and Ohm’s Law

Remember:

E = EMF, or voltage

I = intensity of current, or amperage

R = resistance in ohms

P = power in watts

E (volts) = I (amperes) x R (ohms)

P (watts) = I (amperes) x E (volts)

Unit 2

Electrical Quantities and Ohm’s Law

Metric Units

Unit 2

Electrical Quantities and Ohm’s Law