principles of technology waxahachie high school

Principles of TechnologyWaxahachie High School

Principles of TechnologyWaxahachie High School

Energyin

Electrical Systems

PIC Chapter 5.3

Energyin

Electrical Systems

PIC Chapter 5.3

PT TEKS PT TEKS

Energy in Electrical SystemsEnergy in Electrical Systems

Objectives:

Describe a capacitor.Explain how a capacitor stores energy.Define capacitance.Calculate the electrical energy stored in a capacitor.Describe an inductor.Explain how a conductor stores energy.Calculate the electrical energy stored in an inductor.

Objectives:

Describe a capacitor.Explain how a capacitor stores energy.Define capacitance.Calculate the electrical energy stored in a capacitor.Describe an inductor.Explain how a conductor stores energy.Calculate the electrical energy stored in an inductor.


A capacitor is an electrical device that stores energy in an electric field.

A power supply removes electrons from one plate in a capacitor and deposits them on a second plate.

A capacitor is an electrical device that stores energy in an electric field.

A power supply removes electrons from one plate in a capacitor and deposits them on a second plate.


This causes the plate that loses electrons to become positively charged and the plate that gains electrons to become negatively charged.

The work done to create this electric field is equal to the potential energy stored in the field.

This causes the plate that loses electrons to become positively charged and the plate that gains electrons to become negatively charged.

The work done to create this electric field is equal to the potential energy stored in the field.


Equation for Potential Energy in an electric field =

½ x charge x Voltage

W = ½ q V

Equation for Potential Energy in an electric field =

½ x charge x Voltage

W = ½ q V


If the charge is 10 C (coulombs) and the change in Voltage is 6 V, what is the work done?

W = ½ q x V

W = .5 x 10 x 6

W = 30 J

If the charge is 10 C (coulombs) and the change in Voltage is 6 V, what is the work done?

W = ½ q x V

W = .5 x 10 x 6

W = 30 J


The charge on either plate of a capacitor is equal to the Capacitance x voltage

Capacitors have fixed values of capacitance.

The charge on either plate of a capacitor is equal to the Capacitance x voltage

Capacitors have fixed values of capacitance.


The symbol C is used to represent capacitance.

Charge of a plate in a capacitor = Capacitance x voltage

q = C x V

The unit for capacitance is the farad (F).

1 farad = 1 coulomb per volt, or 1 F = 1 C/V

The symbol C is used to represent capacitance.

Charge of a plate in a capacitor = Capacitance x voltage

q = C x V

The unit for capacitance is the farad (F).

1 farad = 1 coulomb per volt, or 1 F = 1 C/V


If the Capacitance is .0005 F (500 µF) and the Voltage is 200 V, what is the charge?

q = C x V

q = .0005 F x 200 V

q = .1 C

Most capacitors are measured in microfarads (µF) or picofarads (pF)

1 µF = 10-6 F 1pF = 10-12 F

If the Capacitance is .0005 F (500 µF) and the Voltage is 200 V, what is the charge?

q = C x V

q = .0005 F x 200 V

q = .1 C

Most capacitors are measured in microfarads (µF) or picofarads (pF)

1 µF = 10-6 F 1pF = 10-12 F


Potential energy in a capacitor =

½ (Capacitance) (Voltage)2

PE = ½CV2

Potential energy in a capacitor =

½ (Capacitance) (Voltage)2

PE = ½CV2


If the Capacitance is .0005 F and the Voltage is 200 V, what is the Potential Energy stored?

PE = ½CV2

PE = .5 (.0005)(200)2

PE = .5 (.0005)(40,000)

PE = 10 J

If the Capacitance is .0005 F and the Voltage is 200 V, what is the Potential Energy stored?

PE = ½CV2

PE = .5 (.0005)(200)2

PE = .5 (.0005)(40,000)

PE = 10 J


If an electric charge is moving, it will create a magnetic field.If an electric charge is moving, it will create a magnetic field.


Magnetic field lines with the electric current in the center:

Magnetic field lines with the electric current in the center:


If two currents are in the same direction, the wires are attracted.If two currents are in the same direction, the wires are attracted.


If two currents are in opposite directions, the wires are repelled.If two currents are in opposite directions, the wires are repelled.


The Earth’s magnetic field is caused by currents in the molten iron core found at the center of the earth.

The Earth’s magnetic field is caused by currents in the molten iron core found at the center of the earth.


The Earth’s Magnetic Field causes the Northern Lights by attracting electrically charged particles given off by the sun.

The Earth’s Magnetic Field causes the Northern Lights by attracting electrically charged particles given off by the sun.


A magnetic field can also create an electric field. This is called electromagnetic induction (EMF).

A magnetic field can also create an electric field. This is called electromagnetic induction (EMF).


If a loop of wires moves through a magnetic field, a current is produced in the wire.

If a loop of wires moves through a magnetic field, a current is produced in the wire.


To increase the electricity created by a magnetic field:• Use a larger magnet• Use a coil (wire) with a larger diameter• Use more turns of the wire• Move the magnet faster

To increase the electricity created by a magnetic field:• Use a larger magnet• Use a coil (wire) with a larger diameter• Use more turns of the wire• Move the magnet faster


A capacitor stores energy in an electric field and an inductor is an electrical device that stores energy in a magnetic field.

A capacitor stores energy in an electric field and an inductor is an electrical device that stores energy in a magnetic field.


The amount of energy that an inductor can hold is called inductance.

Use the symbol L to represent Inductance and the unit is the Henry.

Equation for EMF =

-inductance (current/time)

EMF = -L (I/t)

The amount of energy that an inductor can hold is called inductance.

Use the symbol L to represent Inductance and the unit is the Henry.

Equation for EMF =

-inductance (current/time)

EMF = -L (I/t)


A coil with an inductance of .0045 Henrys and a current of 1000 amps for 2 seconds. What is the EMF?

EMF = -L (I/t)

EMF = -.0045 (1000/2)

EMF = -.0045 (500)

EMF = -2.25 V

A coil with an inductance of .0045 Henrys and a current of 1000 amps for 2 seconds. What is the EMF?

EMF = -L (I/t)

EMF = -.0045 (1000/2)

EMF = -.0045 (500)

EMF = -2.25 V


Potential energy in inductors (Equation) =

½ inductance (current)2

PE = ½ L I2

Potential energy in inductors (Equation) =

½ inductance (current)2

PE = ½ L I2


A coil with an inductance of 8 Henrys and a current of 15 A has how much PE is stored?

PE = ½ L I2

PE = ½ (8) 152

PE = ½ (8)(225)

PE = 900 J

A coil with an inductance of 8 Henrys and a current of 15 A has how much PE is stored?

PE = ½ L I2

PE = ½ (8) 152

PE = ½ (8)(225)

PE = 900 J

principles of technology waxahachie high school

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