1. Electromagnetic Devices
Electromagnetism is used in many devices – they all involve converting electrical energy into mechanical energy (or vice versa)
galvanometers
motors
speakers
Galvanometers use the strength of an electric current to move a pointer along a dial
Can be used to detect small amounts of current
Used for gas gages and other instrumentation

2. Electromagnetic Devices
Electric motors use the force exerted on a current-carrying wire in a magnetic field to produce rotary movement
(Generators are the same physical device but motion is the input and electricity is the output)
Loudspeakers use variations in electric current to push/pull an electromagnet connected to a diaphragm producing sound waves
(What device is physically the same but has sound as the input and electricity as the output?)

3. Electromagnetic Induction
Electromagnetic induction occurs when a wire is placed in a changing magnetic field
The changing magnetic field “induces” an electric current in the wire
The strength of the electric current is directly related to
How fast the magnetic field changes
How many “turns” or loops there are in the wire
How strong the magnetic field is

4. Generators
Generators are devices that convert mechanical energy (motion) into electrical energy (current) using electromagnetic induction
Depending on their construction, generators can produce either
Direct current (DC) – one-way current, or
Alternating current (AC) – two-way current

5. Transformers
Transformers are devices that increase or decrease the voltage of an electric current using electromagnetic induction
Transformers only work with alternating current!!
Step-up transformers increase the voltage
More wire turns on the secondary (output) coil
Step-down transformers decrease the voltage
More wire turns on the primary (input) coil

6. Transmission of Electricity
The transmission of electric power depends on voltage and current (P = V x I)
But high current causes higher wire temperatures and increases energy loss during transmission
So electricity is transmitted at high voltage (low current)
At the power plant, step-up transformers increase the voltage for transmission
At your home, step-down transformers decrease the voltage for your use