UWCSEA Additional Science P7 - Electromagnetism Flashcards

Flashcards based on lecture notes covering electromagnetism, magnetic fields, electric motors, generators, transformers, and environmental impacts.

What is a magnetic field?

A region of space where a magnetic pole experiences a force.

How is the direction of a magnetic field defined?

As the direction of the force on a north pole.

What induces a magnetic field?

Movement of charge.

What induces an electromotive force (EMF) in a conductor?

Movement of a conductor inside a magnetic field.

What happens to a current-carrying conductor within a magnetic field?

It experiences a force.

Sketch and interpret field line diagrams around what?

A bar magnet, single conducting wire, and solenoid.

Determine the direction of the magnetic field around what?

A single wire and coil of wire.

Determine the direction of what induced in a conductor moving in a magnetic field?

The EMF.

Exaplain the factors that affect the magnitude of the induced what?

EMF.

Determine the direction of the force on what within a magnetic field?

A current carrying wire.

What is the equation for force on a wire in a magnetic field?

F=BIL

How is electricity generated in a thermal power plant?

Heat boils water, steam turns a turbine, which turns a generator.

What is the difference between AC and DC?

AC is alternating current, DC is direct current.

Give examples of household sources of AC and DC

AC: Wall outlet. DC: Batteries.

What are the basic components of an electric motor?

A coil, a permanent magnet, and a power supply.

What do split ring commutators enable?

Direct current to power an electric motor.

What are the basic components of a generator?

A coil and a permanent magnet.

Steps up or down voltage, this electrical term has what?

A coil.

How can energy losses be reduced in transmission?

Step-up transformers increase voltage and decrease current.

How is electricity made usable in homes?

Step-down transformers decrease voltage and increase current.

What is the purpose of transformers?

To adjust the voltage-current ratio.

Energy loss in cables is proportional to what?

The square of the current which passes through them

What is the formula relating primary and secondary voltage to number of turns?

𝑉𝑆/𝑉𝑃 = 𝑁𝑆/𝑁𝑃

What is the equation for resistive losses in a cable?

P=I²R

What is a supply chain?

The sequence of processes involved in making a product.

What are some environmental impacts of technologies?

Extraction of raw materials, transport, manufacture and disposal.

What is required when evaluating the overall environmental impact of technology

consideration of its entire supply chain and life cycle

What is aurorae caused by?

Solar wind and the Earth's magnetic field

What is a magnetic field?

A region of space where a magnetic material experiences a force.

What is a pole?

The part of a magnet where the magnetic field is the strongest.

What do magnetic field lines show?

The direction of a magnetic field (always N to S).

What is induced magnetism?

When a piece of unmagnetised magnetic material becomes a magnet when near a permanent magnet.

What is an electromagnet?

A coil of insulated wire wrapped around an iron core that becomes magnetized when current flows.

What is the motor effect?

When a current-carrying wire in a magnetic field experiences a force.

What is a motor?

A device involving rotating coils of wire which transform electrical energy into mechanical energy.

What is electromagnetic induction?

A voltage is induced when there is a changing magnetic field near a conductor.

What is a generator?

An electromagnetic device which transforms mechanical energy into electrical energy.

What is a transformer?

A device used to transfer electric energy from one circuit to another.

What are the three primary ferromagnetic elements at room temperature?

Iron, cobalt, and nickel.

Why is steel a common ferromagnetic material?

Steel is an alloy containing iron.

What describes the property of 'hard' magnetism?

magnetism is more fixed/ difficult to change.

Explain induced magnetism.

A magnetic field causes the magnetic domains of a non-magnetized material to align.

What is a domain in the context of magnetism?

A little group of atoms that act like tiny magnets.

Why doesn't a normal piece of iron act like a magnet?

Because all the domains are magnetised in different directions. They cancel each other out.

Describe two ways of making a magnet.

Stroking it in one direction or leaving it next to another magnet.

What happens if you break a magnet in two?

The two halves would both be magnets, each with a north pole and a south pole.

How can you destroy a magnet?

Hammer it, heat it, or wrap a coil around it and pass alternating current (AC) through it.

What do magnetic field lines represent?

The direction of force that would act on a North pole.

Where is the magnetic field strength strongest?

Where the field lines are closest together.

What creates earth's magnetic field?

Movement of molten iron and nickel in its outer core

What part of the bodywork of a car needs to be replaced if it rusts?

Steel

What is plastic filler classified as?

non-ferrous

Why is aluminium chosen over steel for cars?

light weight

What happens when a piece of unmagnetised iron is brought close to a suspended permanent magnet?

Attraction, the Magnet will swing towards the iron.

What general rule of magnetism is shown by bringing a magnet to another magnet?

Opposite poles attract, like repel.

What happens to gold, aluminium, and copper when next to a magnet?

no effect

Who discovered that an electric current flowing through a conductor generates a magnetic field?

Hans Christian Ørsted

What is the shape of the magnetic field around a straight wire?

circular fieldlines

How does magnetic field strength change with distance from the wire?

decreases

What is the shape of the magnetic field around a solenoid?

From afar, it resembles a bar magnet.

Where is the magnetic field strongest within a solenoid?

in same direction evenly spaced same strength

Name the forces produced by the two wires.

Repulsion to the right

What happens when a current-carrying wire is in a magnetic field?

The wire experiences a force.

What happens if you change the direction of the current?

Field lines cannot overlap so push against one another

What is the energy transfer for the motor effect?

Electric to Kinetic

What happens to the force if the current is bigger?

The force changes direction if either the magnetic field or the electric fields are reversed.

State LHR motor rule

thumb, index finger, middle finger.

When the coil is horizontal, why is it spinning?

the current isflowing in oppositedirections separation to magnets

When the coil is vertical in the field, there is no force acting on the coil. Why

The current wire is not cutting the field lines

The dc motor 11. State that a current-carrying coil in a magnetic field experiences a turning effect and that the effect is increased by:

ー increasing the number of turns on the coil ー increasing the current ー increasing the strength of the magnetic field.

Where are split rings commutators positioned in a DC motor

They've changed position graphite brushes

What does the commutator do to the current within the coil?

reversed everyhalf turn

Function of the brushes in a DC motor

current intothemotor

Suggest reasons why this set of DC motors might spin the other way

Reversethe current of the magnets/hand side anddown on theright

List a few ways to increase the size of the force produced on motors?

Higher current strongerfield/more turns coils magnets on rotatorcoil

Why is force on each side of the motor coil equal in opposite directions?

the interaction of magnetic fields

what is another term for DC motor

Smoothly contact conduct current

How do brushes and commutator interact in a DC motor?

Ensurethecurrentalwaysflowsthe samewaywiththemagneticfield

Increasing something will ensure some things are proportional

2X current 2X Force induced

What keeps coil turning so it makes contact with brushes again?

Momentum

Why use stronger magnets - what does it increase?

Current?

F

The force on a wire

B

The magnetic field strength

I

The conventional current

L

The length of the wire in the magnetic field.

What are the units for length

metres

What is the unit for Tesla?

[mag field strength] magnetic field strength

what is the unit for AMPS measured as

current measured in conventional current

What is the force on a piece of wire calculated as

0 newtons measured

What does BILxs.no equal?

l/lefthandrule/F

How to solve what Electromagnetic induction is.

The wire charges must experience a changingmagne//7m field B Current/ OR voltage detected.

What must happen to charges

Knetic electrical parallelmotion

Faraday’s Law of Electromagnetic Induction

Whenever there is a changing magnetic field. Near a conductor an emf or voltage is induced

Which way does one change there motion faster if there is changing

Move the rod faster//E1

There moterrule

Flemings lefthand

So there charge cuttingthemagneticfield

an induced emf. Lower resistance.

An AC generator is a

An AC generator is a device that induces an emf.

Thecoil is cuttingthrough the

The rotatorcoil is now cutting thefield lines in/cuttingthrough thefields at the greatest

Why is current opposite direction//compared to the first example shown//in AC GENERATORS?

The rotatorcoil is now cuttingthefield lines in/00theopposite directionso theinduced currentflows theother way//AlternatingCurrent AC

In the AC graph what shape is shown

Kmetre electrical