- Hi, I'm Mattias and this is Hattie,
and welcome to StudyTime's Level 2
Electricity and Magnetism
exam strategy video.
- This exam focuses on the science
behind electricity and magnetism.
Where there's two separate phenomena
and together as electromagnetism.
It's really important for
understanding the behavior
of everyday objects,
and it's also ones of the
oldest branches of physics.
Think of lightening.
The main concepts you'll
be covering at Level 2
are static electricity, DC electricity,
and electromagnetism.
- The questions you'll
be expected to answer
are a mixture of calculation
and explanation questions.
The calculations at merit and excellence
will often involve multiple steps.
And the explanation questions
usually involve how a system will change
when a change is made
- Typically there are three
to four questions on the exam,
and those questions will be
broken down into little sub-parts.
That's quite a lot to answer in an hour,
so you'll want to make sure
that you're really on top of your game.
To make sure that you
can do that in the exam,
we really recommend practicing
under timed conditions.
So, sit down for an hour with a paper,
and make sure that you
can answer the whole paper
in that hour.
In the actual exam, keep
your eyes on the exam clock
to make sure you're
managing your time well.
- The nice thing about the
Level 2 electricity topic is
that each question is usually
an individual concept.
For example, you may have a
single question on DC circuits
that involves components of calculating
things to do with the circuit,
and then explaining what happens
when something in the circuit changes.
Make sure you know how
voltage and current behave
in a circuit, both in
series and in parallel.
In addition, you may be required
to draw circuit diagrams,
so make sure you know what
each component looks like,
and how to draw a series
and parallel circuits.
For the description part,
you will be expected to
discuss how something changes
when you make a change in the circuit.
For example, how does the
brightness of a bulb change
when the resistance increases?
Well, if the resistance increases,
that means the current drops,
which means the power
delivered to the bulb is less,
which means the bulb is less bright.
- There'll also be a question
on either the motors or the generators.
These can either be calculation-based
or conceptual-based.
And conceptually,
they're one of the more
difficult parts of the topic,
but it's absolutely fundamental knowledge.
They will usually be put
into a practical context
like a motor in a car.
So the idea is,
that if you run a current
through a wire in a magnetic field
then a magnetic force will
be induced on that wire
and that will cause it to move.
That's called the motor effect.
A generator is when you want
to actually induce a current.
So, that's what you move a
wire through a magnetic field
and that causes a -- to move
in the wire, causing a current.
- Every year, NCEA publishes a list
of common mistakes that
students make in the exam.
So here's a few that you
shouldn't do in your exam.
Often students couldn't
tell the difference
between a magnetic field
and an electric field.
Remember that an electric
field is created by
the separation of charge,
be it charged plates or charged wire.
A magnetic field, on the other hand,
is usually created by a permanent magnet
or by chargers moving through a wire.
Another really common mistake
is students not using SI
units in their calculations,
and in their answers.
For example, converting
millicoulombs into Coulumbs.
A really good study strategy
here is to make a large table
of all of the quantities and the SI units,
so that you know how to
convert them to the SI units
in order to get the correct calculations.
- Another thing that
came up really commonly
is that students had trouble
choosing the correct formula
to answer a question.
Like all the physics
standards, this one involves
a lot of different formulas,
and they can be really confusing
if you're not properly familiar with them.
We'd recommend knowing what
each symbol stands for,
what unit it's measured in,
and also what context to use it in.
And a really good way of doing this
is to put them all in
a big mind map at home
and annotate them with things like,
"what does this symbol mean?
When would I use this?"
Another mistake that will come up
is that people will use the
right hand rule incorrectly.
Really the only way to get around this
is to make sure you're using it at home
when you're doing practice questions,
and probably make sure that you
don't use your left hand instead.
- We'll now run over some important
but often really difficult concepts.
First is being able to calculate
the total resistance of a circuit
both in series and parallel.
The way that I like to
remember which formula to use
is that in series, you're just adding up
each of the resistances, but in parallel,
you've got a resistance over a resistance.
So you have to use the formula that has
1/Rt = 1/R1 + 1/R2, so on and so forth.
Another tricky concept is the
idea of conventional currents.
You have Benjamin Franklin
to thank for this.
Before they knew about electrons,
it was just assumed that current moved
in the positive to negative direction.
You can tell because of the positive
and negative terminal of a battery.
In reality, we know that
electrons are repelled
from the negative plate of the battery
so they move from negative to positive.
In general, the direction of the current
in Level 2 is conventional current,
but when they ask about
the direction of electrons,
you use the opposite.
Another really important convention
is the direction of magnetic fields.
We use an x to denote a magnetic field
that's going into the page,
and a dot to denote a magnetic field
that's coming out of the page.
The way that I remember
this is by using an arrow.
If you fire an arrow into a page,
you see the tail fins, but
if an arrow's flying at you,
you see a point.
- You also want to make sure
that you're super confident
with all the terminology in this exam.
Cause you can be thrown
some really tricky explanation questions.
The best way to make sure you have time
to answer these fully is to be
really confident with the basics.
People often get little bits
of terminology mixed up,
for example, you need to
make sure you can distinguish
in your mind that current
is the flow of electricity
across a conductor, and voltage
is the potential difference
across a component in the circuit.
Any time you're doing a
practice question at home,
especially if the word is
bolded in the question,
you should note that down and make sure
you know the definition of it,
so that they are familiar to you
when they crop up in the exam.
- Like the other Level
2 physics standards,
merit and excellence
questions often involve
multiple steps for calculations.
Again, a really good strategy
is just to write down
everything that you know
about the scenario, and then write down
what you're trying to find.
You usually won't have a single equation
that allows you to get to the final answer
but you may have to use two or three
different equations to get there.
So, write down any equations
that you think are relevant
and try calculate the quantities
that will eventually get
you to the final answer.
It may take a little bit
of out of the box thinking
and a little bit of problem solving,
but if you practice them enough,
you'll get there in the end.
We've covered some really
important parts of the content
and strategies to approach it,
but we haven't covered everything.
So make sure you check out
the last three or four years
of past exams to figure out
exactly what you may be asked.
- We'd also recommend checking out
the Study Time walkthrough guides.
They're available for free online
or to purchase in print,
and are designed to walk you through
all the content that you
will need for this exam.
You'll be all set to ace it.
Good luck!
- Good luck!
