Electricity and Magnetism

Electricity and Magnetism

​Electrons & Protons

• For your information...

• Electrons have a negative charge.

• Protons have a positive charge.​

Electric Charges

• ​ With an electric charge, it causes electrons and protons to exert forces on one another.

• ​ Particles with like charges repel one another.

• Particles with unlike charges attract each other.

• Sometimes electrons are temporarily pulled away from atoms, creating stationary areas of positive and negative charges.

• This is called static electricity

​Currents

• ​ The movement of charged particles, usually electrons, is an electric current.

• Direct current flows in one direction only, and it is used in battery operated devices.

• Alternating current flows back and forth rapidly​, and it is used in household wiring.

• A material that allows electrons to move freely from atom to atom is called a conductor. (aluminum and copper)

• ​ A material that does not allow electrons to move freely from atom to atom is called an insulator. (rubber and plastic)

• Semiconductors are in the middle of conductors and insulators. (silicon)

​Magnets

• An electric current produces a magnetic field that affects magnetic substances such as iron in the same way a permanent magnet does.

• Magnetic fields are produced by charged particles​. A particle is charged when it loses an electron.

• ​In an electromagnet, the charged particles move along a coil of wire connected to a battery or other power source.

• In a permanent, the spinning of electrons creates a magnetic field.

• Every magnet has 2 ends, called north and south poles.

• The north pole of one magnet attracts the south pole of another magnet; like poles repel one another.​

• ​Just as an electric current produces a magnetic field, a moving magnetic field produces an electric current.

• This principle underlies electric motors, generators, and transformers

• In an ​electric motor, magnetic fields are produced by electric currents. The magnetic fields push against one another, turning the shaft of the motor.

• In a generator, a moving magnetic field produces electric currents.

• In a transformer, an incoming electric current in coiled wire produces fluctuating magnetic fields, which in turn produce an outgoing electric current of a different voltage.

• The difference in voltage is caused by the differing sizes of the wire coils.​

​Electronic Devices

Multiple Choice

Suppose a drawing of two magnets with their north and south poles facing one another were added to the picture. What would the new diagram show?

• Two poles attracting one another.

• Two poles repelling one another.

• Magnetic lines of force connecting the poles.

• Magnetic lines of force flowing southward.

Multiple Choice

What is the reason copper and aluminum are used for electrical wiring?

• Copper and aluminum are conductors.

• Copper and aluminum are insulators.

• Copper and aluminum are semiconductors.

• Copper and aluminum are magnetic.

Multiple Choice

Which or the following devices most likely uses a direct current?

• Washing machine

• Desktop computer

• Toaster

• Flashlight

Multiple Choice

In an electric power plant, generators may produce electric current at about 10,000 volts. The current may be stepped up and transmitted along high voltage lines at 230,000 volts, and then stepped down to about 2,300 volts for transmission in a city. Finally, before it enters houses, the current is stepped down to 110 volts.

Which of the following devices steps current up and down for efficient transmission?

• A conductor

• An electromagnet

• An electric motor

• A transformer

Multiple Choice

Which element in the diagram acts as a resistor in the circuit?

• The light bulb

• The switch

• The wire

• The 9-volt battery

Multiple Choice

A student was asked how the current in the circuit could be stopped without using the switch. He answered that the only way to stop the current was to disconnect the battery.

What was wrong with the students response?

• Disconnecting the battery will not stop the current.

• Removing the fuse will also stop the current.

• Disconnecting the lightbulb will also stop the current.

• There is no way to stop the current without using the switch.