El. motors
Name the force that the operation of an electric motor is based on, and is a scientist's last name.
Ampere's force
What popular Christmas decorations use AC current and convert electrical energy to light energy?
Christmas lights
This device ensures your outdoor Christmas light display gets the right voltage by stepping down the high household voltage to a safer, lower level.
A transfromer
Many Christmas light displays are powered by electricity from these types of power plants, which often work overtime during the holidays to meet the increased demand.
Coal or hydroelectric powerplant
Who created the first electric Christmas light display, replacing dangerous candles with safer electric bulbs.
Thomas Edison (and Edward H. Johnson Edison's friend and partner in the Edison's Illumination Company )
Describe a Christmas decoration that uses a small motor.
A spinning carousel
A spinning ballerina in a musical box
This is the unit used to measure the frequency of an alternating current.
Hertz (HZ)
Transformers work on this fundamental principle
Electromagnetic induction
In most power plants, this device converts rotational kinetic energy into electrical energy.
A generator
This inventor is credited with developing the first practical AC motor
Nikola Tesla
Outline the energy conversion that happens in an electric motor.
Electric energy is converted into mechanical energy.
What is alternating electric current?
It is a current that periodically changes it's magnitude and direction
What is transformer with more turns in its secondary coil than its primary coil called?
A step-up transformer
Name two disadvantages of solar power plants.
Only produces energy when the sun is shining, requires a lot of land
Starting in the late 1880s two scientists who developed AC and DC current were competing for which current should be used in transmission systems (this is called the war of currents). Name the scientists who developed AC and DC currents.
Thomas Edison (DC) and Nikola Tesla (AC)
Outline two ways to increase Ampere's force in an electric motor.
Increase current strength, increase number of turns of wire in the rotor, use a stronger magnet for a stator.
What is the frequency of electric current in Lithuanian electric grid?
50 Hz
If transformer's primary coil of 10 turns is connected to a DC battery of 10V, what will be the voltage in the secondary coil of 100 turns?
0
Name the fundamental principle that the operation of an AC generator is based on.
Electromagnetic induction
When was the first electric powerplant in Lithuania built?
In 1982 in Rietavas
Outline two ways to change the direction of rotation of an electric motor.
Change the direction of current flow, change the polarity of stator magnets.
In your own words explain what does the value of effective electric current show
It shows what strength of direct electric current would be needed to transfer the same amount of energy as AC current
Transformers are used in electric grids to reduce energy lost over transmission lines. Explain how transformer helps to reduce energy loss.
Transformer increases voltage of AC current which in turn reduces the current strength and it reduces energy lost as heat. (Q=I2Rt)
Explain why the direction of current produced by a generator is periodically changing direction?
Because as the generator spins the rotor wires change the direction of movement every half a rotation and the direction of induced current depends on direction of movement
Lithuania’s first hydroelectric power plant, Kaunas Hydroelectric Power Plant, began operation in this year
1959