Simple Circuits & Ohm's Law
What is the formula for Ohm's Law?
V = IR
Voltage (in volts) = Current (in amps) x Resistance (in ohms)
Electromagnetism is the interaction between what two things?
Electric charges and magnets
What main part of an electric motor is a coil of wire shaped like a letter "T" that rotates?
armature/rotor/electromagnet
Electrically charged particles only produce a magnetic field if they are ___________ in a current-carrying wire.
moving
What two scientist were early promoters of direct current (DC) and alternating current (AC) in the late 1800s?
Thomas Edison was a promoter of direct current (DC), and Nikola Tesla was a promoter of alternating current (AC)
The device in a circuit which is being powered by the circuit is known as the ______________.
load
Electromagnets often contain a compressed coil of wire designed to maximize the number of coils or loops in it. What is this known as?
A solenoid
Most electric generators today are powered by which two ways?
Mechanical energy by motion from a hand crank and chemical energy by using gasoline
Any device that plugs into an electrical outlet to run runs on what kind of current?
alternating current (AC)
The two permanent magnets found on each side of the rotating wire coil in both electric motors and electric generators are known as _____________.
stators
A circuit has a voltage of 240 volts and a resistance of 3 ohms. Calculate the amount of electric current in the circuit.
80 amps
240 volts / 3 ohms = 80 amps
What are three ways that electromagnets are more useful than permanent magnets?
They can be switched on and off, their strength can be increased or decreased, and their polarity can be reversed.
What is the purpose of a commutator ring or rings in electric motors and generators?
They reverse the current in the wire coil as it spins in order to keep the wire coil spinning. Without them, we'd have to manually reverse the conducting wires or power source constantly.
What are three examples of objects that run on direct current (DC)?
Smartphones, laptops, & smartwatches
Any kind of portable electronic device runs on direct current (DC).
How is having more coils or loops in a current carrying wire similar to having more twists and turns in a person's small intestine?
Your small intestine is shaped in a twisting and turning pattern to increase the amount of nutrients absorbed from your food as it passes through your body. Similarly, the a current-carrying wire is shaped into a solenoid to increase the magnetic field strength over a given distance by combining all of the individual magnetic fields of each individual coil.
What is the difference between an open circuit and a closed circuit?
An open circuit has a break in it and is not complete so electricity can't fully flow through it. A closed circuit is complete and electric energy can flow through it.
In what four ways can you increase the strength of an electromagnetic current?
Use a stronger magnet, include more coils in the conducting wire, increase the speed or motion of the magnet, and have the magnet aligned more perpendicular
What could be attached to the axle in an electric motor, and what could be attached to the axle in an electric generator?
In a motor, this is where a gear, a wheel, or any other object that can spin would be attached. In a generator, this is where a hand crank or a gas chamber would be attached.
If a compass were held parallel to a current-carrying wire, what would happen to it and why?
Nothing would happen to it because the magnetic field around a wire perpendicular to the current, not parallel.
The first electric generators were powered by hand crank. However, most modern generators are now gas-powered instead. Why is this?
Gas powered generators can run for much longer since a person turning a hand-crank generator will eventually get tired and run out of energy to turn the hand-crank.
Explain why switches are a convenient addition to a circuit.
Switches allow us to easily open and close a circuit quickly. Without switches, we'd have to manually disconnect and reconnect parts of the circuit any time we wanted it on or off.
Why are electromagnets so useful to our daily lives, and what are three examples of technology that include electromagnets?
The vast majority of technologies we use today have electromagnets in them. They are used to generate motion or electricity in several of these devices. Some examples of everyday technology that include electromagnets are ceiling fans, electric motors, smartphones, and computers.
Electric motors and generators are very similar, but they have one key difference. What is similar about them, and what is this key difference?
Electric motors and generators use all of the same parts (armature/rotor/electromagnet, axle, stators, commutator ring/rings, metal brushes, and conducting wires). However, the key difference between them is the input and output for each of them. In a motor, you input electrical energy from a power source and output motion. In a generator, you input motion or chemical energy and output electrical energy.
Why is alternating current (AC) used to power most homes and businesses today?
The voltage of it can easily be stepped up or down using transformers since it is constantly changing directions. Because of this, it is safer and more cost-efficient to use than direct current (DC).
When Nikola Tesla came to the US and worked for Thomas Edison, he discovered a safer, more cost-efficient way to carry electric current long distances through wires. What was Thomas Edison's response to this and why?
Thomas Edison fired him and did everything he could to disparage Tesla and his newly discovered method of carrying electric current. He did this because he saw Tesla and his new method as a threat to his already well-established business promoting his method of carrying electric current.