01BASCI

E P G I

-0I- BASIC ELECTRICITY

- COMPARISON

- OHM FORM

- SERIES CIRCUITS

- PARALLEL CIRCUITS

CIRCUIT

TYPICAL ELECTRICAL

CIRCUIT

I

LOAD

SOURCE

TYPICAL HYDRAULIC

CIRCUIT

SOURCE

LOAD

Q

• Voltage Source (battery) • Conductors (wire)

• Load (resistor, lamp, etc.)

Current Flow

• Measured in ampere • Symbol is "I" (intensity) • The movement of electrons

Positive Source

• Battery (generates DC voltage) • Produces certain voltage

regardless of the load

Circuit

• Pressure Source (pump) • Tubing, hoses

• Load (hydraulic cylinder)

Oil Flow

• Measured in gpm, cfm, L/min • Symbol is "Q" (quantity) • Movement of fluid molecules

Positive Source

• Pump (when pump shaft is rotated, fluid is positively expelled from the output port, no matter how restrictive the load)

OPPOSITION

+

-High

Low

I

High

Low

Q

RESISTOR

ORIFICE

Vd

∆

P

Opposition to Current Flow Resistance

• Opposes current flow • Measured in Ohm • Symbol is R or Ω

• Dependent on length, diameter, material and temperature

Opposition to Oil Flow Resistance

• Opposes oil flow

• Measured in psi, kPa, L/min • Symbol is P

• Usually measured as a pressure drop (∆P) in a hydraulic circuit

STORING

Gas

Oil

Piston

Fluid Input

Plate

Plate

Dielectric

CAPACITOR

ACCUMULATOR

• Stores electrical charge • Measured in Capacitance • Symbol is C

• Unit is Microfarad (µF) • Pair of conductors separated

by a dielectric material

Storage Devices

• Develops and stores pressure • Measured in pressure

• Stores pressure as a result of forcing a volume of oil into a accumulator chamber

DIRECTIONAL

+

-DIODE

CHECK VALVE

• Current flows in one direction • Current flows when anode is

more positive than the cathode • Use multimeter on "diode check"

function and measure voltage drop

Directional Controls

• Fluid flows in one direction • Symbol indicates direction of

OHM FORM

Ohm's Law

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

The above formulas will be used when describing electric and electronic circuits. Three types of electrical circuits will be discussed.

• Series Circuits

- Current can flow in only one path.

• Parallel Circuits

- Current can flow in more than one path.

• Series-Parallel Circuits

UNKNOWN CALCULATION

I

E

R

=

E

I

R

E I x R

=

E

I

R

R

E

I

=

E

I

R

Given two known in any electrical or electronic circuit, the unknown can be calculated. This slide shows an example of solving an unknown by placing a finger over the unknown and then performing the

mathematical equation as shown.

CALCULATE

A

Filament Resistance = 60

Ω

I = 200 mA

E = _____

?

E I x R

=

E

I

R

CALCULATE

A

Filament Resistance = _____

Ω

I = 600 mA

?

E = 12V

R

E

I

=

E

I

R

CALCULATE

A

Filament Resistance = 240

Ω

I = ____ mA

?

E = 24 V

I

E

R

=

E

I

R

SERIES CIRCUITS

POS NEG

POS NEG

R1

R2

R3

12V

12V

• Sum of all voltage drops equal source voltage

• Current flow through each load is the same

• Total resistance is equal to sum of all the resistors

Series Circuits

Series circuits may have several resistors (loads) connected to a voltage source. The important point to demonstrate when explaining series circuits is current flow which has only one path, and as such, the current flowing in the circuit passes through all resistances equally.

Series circuits have the following features:

• The current through each resistor is the same.

• The voltage drop across each resistor will be different if the resistance values are different.

CALCULATE

POS NEG POS NEG

R1

R2

R3

12V

12V

8

Ω

24

Ω

16

Ω

V1

V2

V3

A

• Total circuit resistance = the sum of all the resistors or 8 + 24 + 16 = 48Ω

• Source voltage = the sum of the two batteries (connected in series) or 12 + 12 = 24V • Current flow = source voltage divided by total resistance or

CALCULATE

POS NEG

POS NEG

R1

R2

R3

12V

12V

6

Ω

___

?

Ω

4

Ω

CALCULATE

POS NEG

POS NEG

R1

R2

R3

12V

12V

6

Ω

2

Ω

4

Ω

?

CALCULATE

POS NEG

POS NEG

R1

R2

R3

12V

12V

6

Ω

₂

Ω

₄

Ω

A

?

unwanted path

PARALLEL CIRCUIT

POS NEG POS NEG

12V

12V

R2

R3

RULES

• Voltage drop across each resistor is the same

• Current flow through each resistor is

different if the resistor values are different

• The sum of the separate currents equals the

total current flow in the circuit

R1

Parallel Circuits

In parallel circuits, the voltage drop across each resistor is equal to the potential of the current source since there is more than one path for current to flow through each resistor.

Parallel circuits have the following features:

• The voltage drop across each resistor (load) is the same.

• The current through each resistor will be different if the resistance are different.

• The sum of the separate currents equals the total current in the circuit.

CALCULATE

POS NEG POS NEG

12V 12V R2 R3 R1 A1

A

3

Ω

6

Ω

2

Ω

• Voltage drop each resistor is the same as source voltage (24V).

• Total current flow is the sum of the separate currents (each path), not enough information to solve individual current flows

without using Ohm's Law to solve other elements of the circuit. • Solve the current flow through each load by using Ohm's Law.

V1 = source voltage (24V) R1 = 3 Ω A1 = E1 ÷ R1 = 24 ÷ 3 = 8 (A1 = 8 amps) V2 = source voltage (24V) R2 = 6 Ω A2 = E2 ÷ R2 = 24 ÷ 6 = 4 (A2 = 4 amps)

PAGE

POS NEG

12V

R2

R1

A1

V1

V2

A

A2

3

Ω

6

Ω

?

PAGE

POS NEG

R2

R1

___

6

Ω

8A

?

24V

CALCULATE

POS NEG

12V

R2

R1

A1

V1

V2

A

A2

3

Ω

6

Ω

?

CALCULATE

POS NEG

R2

R1

___

6

Ω

8A

?

24V

SERIES - PARALLEL

R1

R2

R3

12V

DRAWING EQUIVALENT CIRCUITS IS IMPORTANT IN SOLVING

SERIES-PARALLELS CIRCUITS

EQUIVALENT CIRCUIT STEPS

Re

+ R3 = Rt

Step 2

12V Re R1 x R2 R1 + R2 Re = R1 R2 POS NEG R3 12V Re

Step 1

R1

R2

R3

12V

CALCULATE Rt

6 x 3

6 + 3

Re

=

=

18

9

=

2

2

+ 2 = 4

TOTAL RESISTANCE IS 4 OHM

THEN I = E / R = 12 / 4 = 3 amps

RECONSTRUCTING

12V

R3 = 2

Ω

Re = 2

Ω

Et = 12 volts

I t = 3 amps

Rt = 4 ohms

I3 = 3 A

E3 = I x R = 3 x 2 = 6V

6 volt drop

FINAL CALCULATION

R1

R2

R3

12V

6

Ω

3

Ω

2

Ω

3A

6V

6V

6V

2A

1A