Unit D Section 3.2

Question 1

What are electric motors?

Answer 1

It is an electrical machine that converts electrical energy into mechanical energy.

Ex. Vacuum cleaners have electric motors, because The motor has a fan attached. When it spins, the blades of the fan force air out, which creates suction inside the vacuum cleaner.

Electric motors can make a strong electromagnetic by winding a current-carrying metal wire around a metal core.

Question 2

Electromagnetic

Answer 2

Electromagnetic is a coil insulated wire that becomes a magnet when current flows through it.

an electromagnet will move to line up with the magnetic field from a nearby permanent magnet. Same way two magnets attract.

Question 3

How do you keep an electromagnet spinning in a magnetic field?

Answer 3

The trick is to switch the direction of that the current traveling through the coil just as it aligns with the magnetic field with the permanent magnet.

Reversing the current reverse the front and end of the electromagnet. It will continue turning in order to align the opposite way.

Changing the polarity of the electromagnet every half turn causes the electromagnet to be continuously pushed and pulled by the permanent magnet.

Question 4

Components of electric motors:

Answer 4

1. Electromagnet
2. The commutator
3. But the armature
4. Brushes
5. Magnetic field

Question 5

1. Electromagnet:

Answer 5

Converting a metal to a magnet by passing electricity.

Question 6

2. The commutator:

Answer 6

is a split ring that breaks the flow of electricity for a moment and then reverses the connection of the coil.

When the contact is broken by the commutator so does the magnetic field.

Question 7

3. armature

Answer 7

the armature continues to spin because of its power and strength, velocity.

The armature is the rotating shaft/stick with coil wrapped around it.

Question 8

4. Brushes

Answer 8

-are bars of carbon, pushed against the metal commutator by springs.

They make electrical contact with the moving commutator by “brushing against it”

As a result of the spinning, the commutator reconnects with the brushes. The magnetic force on the coil keeps it spinning continuously.

Question 9

5. Magnetic field:

Answer 9

Magnetic field is the field of attraction between the opposite poles of permanent magnets.

Question 10

How can we increase the strength of a magnetic field?

Answer 10

We can increase the strength of the magnetic field by increasing the size of permanent magnets.

Question 11

How do the components of electric motors work all together?

Answer 11

Current flowing through the wire coil creates a magnetic field around the wire. This interacts with the permanent magnets, making the coil spin

As the coil spins, the commutator changes position so that its other half contacts the other brush. This reverses the current flow at just the right time. The magnetic force is directed on the coil to keep it spinning.

Question 12

Steering Analogy with the commutator?

Answer 12

Ex.Turning a steering wheel is similar to the turning of the armature in a motor

Can you turn a steering wheel with out letting it go?

You can’t because your hands must release and return to their starting position in order to keep turning the wheel. If you don’t let go the wheel can only turn half way. And you will be stuck.

The same problem occurs with the motor. Without the split-ring commutator, the armature would turn only one-half turn, then it would stop, locked into place by magnetic attraction.

Question 13

What are DC motors?

Answer 13

Some motors run on direct current (DC). It’s called “direct” current because the electricity flows in only one direction

Ex. mp3 players, computers, cell phones, and calculators

Question 14

What are AC Motors?

Answer 14

Some motors run on alternative currents (AC).It’s called “alternating” because it flows back and forth 60 times per second.

Ex. the electricity in household circuits is ran by AC motors.

Question 15

Difference between AC and DC motors?

Direct Current

Answer 15

• Electricity flows only one direction.
• Since it’s one direction, provide stable output of electricity
• Cell phones, Calculators and computers.

Question 16

Difference between AC and DC motors?

Alternative Current

Answer 16

• Electricity flows back and forth 60 times per second
• Great for being transmitted over long distances
• Powerlines from power station use AC to transfer electricity to other places.

Question 17

Difference between AC and DC motors?

Alternative Current

Answer 17

• Electricity flows back and forth 60 times per second
• Great for being transmitted over long distances
• Powerlines from power stations use AC to transfer electricity to other places.

Question 18

DC and AC in electrical motors:

Answer 18

The magnetic field from “field coils” which also have AC current.
AC current in coils.

When the electric current passes through a coil in a magnetic field, the magnetic force produces a torque which turns the DC motor.

Question 19

DC as generators:

Answer 19

If you run electricity through a DC generator, it will spin like a motor because it is structurally the same as a DC motor. It has a spinning armature that produces electricity.

Question 20

AC as generators:

Answer 20

The central axle of an AC generator has a loop of wire that is attached to two slip rings

when a wire moves in a magnetic field, current is generated in the wire
the axle and loop of wire turn, one side of the loop moves up, and the other side moves down through the magnetic field. When the wire moves up between the magnets, current flows one way in the wire. But when the wire moves down, the current moves in the other direction = how current switches the direction in the wire with each complete turn in the loop.
The brush and slip ring arrangement allows the whole loop to spin freely
In large AC generators, such as those in a power station, many loops of wire are wrapped around an iron axle-core

Question 21

Transformers:

Answer 21

Devices that help to change the amount of voltage without any energy loss

Question 22

Why do power companies mostly generate with AC

Answer 22

Power companies mostly generate with AC because with AC they can use transformers to change the amount of voltage.

Voltage change is necessary because the most efficient way to transmit current over long distances is at high voltage

This can be reduced before the current can be used in our homes

Question 23

A step-down transformer

Answer 23

reduces the voltage

Question 24

A step up transformer

Answer 24

increases the voltage

Question 25

Primary coil

Answer 25

The current-carrying wire is wrapped around one side of an iron ring called a core

Question 26

A secondary coil

Answer 26

is wrapped around the other side of the core

Question 27

The primary coil and secondary coil importance?

Answer 27

Primary coil influences the current in the secondary coil.

If the number of loops in the two coils is different, the voltage is transformed down or up

Question 28

What is electromagnet induction?

Answer 28

It is a discovery that electrical current could be generated by conducting a wire through a magnetic field.

Question 29

What did electromagnet induction introduce?

Answer 29

This introduced a way to generate a steady supply of large amounts of electricity.

Question 30

Principle of electro magnetic induction:

Answer 30

As long as you keep turning, electricity will be produced

The faster you turn, the more current is generated.