Turning effect on a current-carrying coil

In this learning outcome, it is important 4 u to really understand the whole concept. It represents the fundamental principle of how d.c motors work. In SPM physics , it always being asked in Paper1 or Paper2.
So, in this outcome, u must be able to;

-Describe how a current carrying coil in a magnetic field experiences a turning force:
To describe this, 1st u need a wire(conductor) and shape it like a coil in diagram1.

Diagram 1

Then bring this coiled wire in between a permanent magnet. After that u connect both end of the wire to a battery. As a result,current will be supplied through the coil a-b & c-d as shown in diagram 2.

Diagram 2

- From the diagram2 , current in side a-b & side c-d are in different direction.
- In side a-b, apply Fleming Left hand rule, u'll get a force acting downward.
Thus side a-b will pushed downward.

- In side c-d, applying Fleming left hand rule, u'll get a force acting upward.
This caused side c-d to move upward.

- As a result, a turning effect in both sides turn the coil rotating anticlockwise as shown in
diagram 3 below.

Diagram 3

By looking at different view, the turning effect can also be illustrated in diagram 4.

Diagram 4

Factors Affecting the FORCE

Lets now analyse another learning outcome from subtopic 3.2 electromagnet :

Explain the factors that affect the magnitude of the force on a current-carrying condutor in a magnetic field..

This question can come out in paper 2.. basicallyt if u bring a wire which has current flows in it near to a permanent magnet, the wire will be pushed by a FORCE.

The factors that affect the strength of the force depends on:

1. strentgh of magnetic field
- stronger magnet produces stronger magnetic field,thus the force produced is greater

2. amount of current
- the bigger the current, the greater is the force

3. length of conductor(wire)
- the FORCE increases as the length increase

And again i remind u, this direction of force can be determined using FLEMING LEFT HAND RULE

Revise FLEMMING's LEFT HAND RULE.

Combined Magnetic Field Pattern

Under subtopic 3.2, u also need to know :

How to draw pattern of combined magnetic field due to current carrying conductor in the magnetic field?

Ok,it states the word combined magnetic field..so that means there are more than one magnetic field,which is;


i. magnetic field pattern due to current in the conductor(wire), (refer diagram 1)

Diagram 1

ii. magnetic field pattern from poles of permanent magnet,(refer diagram 2)

Diagram 2

When these 2 magnetic field combine, u'll get a pattern like this..(click the diagram below)


As conclusion, when the current carrying conductor is brought near to a permanent magnet, the two fields will interact to produce a resultant FORCE.

(The FORCE direction can be determined using LEFT HAND FLEMING RULE.)

So, in SPM u must understand & know how to draw those combined magnetic field.
I'll post some questions on this soon, till now, BYE!

SPM F5 3.2: Magnetic Force

The next learning outcome, is getting more interesting. By understanding it, u can create so many cool toys & gadgets such as car & chopper remote control . This subtopic requires a complete understanding on certain rules & principles. Lets go in depth,

3.2: Understanding the FORCE on a current carrying conductor in a Magentic Field.
i. U must be able to describe; What happen to a current carrying conductor in magnetic field?? Hmm... when current flows in a wire which then brought near a magnetic field, a magnetic FORCE will be produced. This force, can be illustrated through a rule called FLEMMING LEFT HAND.


This rule is used to determine the direction of force acting upon it.

Ok... how to use it?
Just treat it like a gun :) aiming towards 2 direction, i.e Current & magnetic field.

1st, u need to determine the current direction, then followed by magnetic field direction. Usually students asked me, how to know the direction of magnetic field??
Its simple, the magnetic field always move from north to south
After u've determine both direction of current & magnetic field correctly, automatically your thumb will be pointing towards the direction of force.
By watching these video,it might help u to understand the concept better.

SPM: Express Revision Notes

Hi there,
Lately, i've been receiving so many request on 'express' revision notes . I think some of u have started to feel the HEAT..followed by the PRESSURE .Well ..that's what SPM is all about :)
Thats y u need to learn PRESSURE in form 4..
In physics ..Pressure = (Force) / (Area)
.. the bigger the force, the larger the pressure
..the smaller the area, the larger the pressure

applying this concept, i can derive a new formula called 'SPM PRESSURE'..

In SPM, ..PRESSURE = (No. of SUBJECT) / ( time)

(No. of subject) can be considered as no. of weight u have to carry, thus if u take more subject, the pressure is getting HIGHER..

As for time, if u have less time or when the time is getting closer towards SPM, the PRESSURE will be mounting HIGHER as well..

To summarize this new formula, if u r studying last minute.. your time is getting lesser. Then i can conclude that "U WILL BE UNDER XTREME PRESSSSURE"
So don't wait until last minute..coz u 've at least 9 subjects to carry, berat tu :)

By the way,here i include those 'Express' notes in powerpoint version. The notes is useful if u wanna have a quick revision. Hopefully it can reduce your pressure :)

My last advice is..please plan your time. Dont procrastinate, coz it is a thieves of time.
I think thats it 4 now..see u in next post, bye & gudluck..

Form4 Express notes:

Chapter 1- Introduction to Physics

Chapter 2- Forces & Motion

Chapter 3- Forces & Pressure

Chapter 4- Heat

Chapter 5- Light

Form 5 Express notes:
Chapter 1- Waves

Chapter 2- Electricity

Chapter 3- Electromagnet

Chapter 4- Electronics

Chapter 5- Radioactive

(Thanx & best regards to the author for publishingg this notes on the web)

SPM Questions: Electromagnet 3.1

SPM Questions on electromagnet: 2004 -05

1 The diagram shows an arrangement of apparatus to study the pattern of magnetic fields which are formed when current flows through conductors:

Answer: B

To answer this one, 1st determine the direction of current entering the cardboard for both conductors.

For each case, apply right hand thumb rules to determine the direction of magnetic field.Look at diagram below:

2. The diagram shows an electromagnet.

Which factor does not influence the strength of the electromagnet ?

A Material used for the wire

B Material used for insulator of the wire

C Number of turns of wire

D Current flowing in the wire..

Answer:B, coz insulator wont affect the magnetic field strength

This question asked for a wrong answer..so beware, always underline important phrase like, does not.

The other answers will influence the strength of electromagnet;

- A: different wire materials used would give dfferent resistance which then affect amount of current flows.

strength of magnetic field depends on current flows.

- C: No. of turns wire...bigger number of turn produce stronger magnetic field

- D:amount of current...higher current give stronger magnetic field

Physics SPM Tips to score 'A'

Since so many students emailed and ask me how to study physics, perhaps in coming month i should share some daily or weekly tips with u, so at least u can grab a 'B' for your physics . I know, some may question me..why not an 'A' . Well.. majorities of students dint do well in their physics. Usually they just passed in their exam or test. Actually, ramai yang 'fail'..this is a fact whether u like it or not. Frankly speaking, for those who wants to get an 'A' i think u must do some extra work . I'll discuss about it later..

Yesterday i went to Pesta buku at PWTC and bought a few books for my home tuition student. See, how lucky they are :)..they dont have to be bother getting stuck in a crowded place. I just do this coz i care about u guys. I want u to do well in your SPM. Hopefully, siapa yang selalu kena 'laser' should understand, its for your own good :).
For those who staying in KL, u should go there and get some exercise books. We're moving towards May 09, tis is time for u to do more & more exercises. Most of the publishers are giving discount, especially kalau u all beli banyak-banyak.

There's one book i want u to have. It is is a koleksi soalan SPM by Cerdik Publications. This book is a must, especially for my followers like Faris Fikri who has the semangat to do well in his physics. If u buy the latest edition,it covers questions from 2005-2008. (Hmm.. may be i should ask CERDIK some commission for recommending their books..haha :)

Here i wanna share one of tips on how to get an A in your physics. From now on, u must familiarize yourself with SPM type of questions. Especially in paper 1 , there seems to be a repetition pattern on certain questions. Let say if u've tried at least 5 passed year paper, i/m sure u can understand what do i mean by a repetition pattern. Kementerian will not repeat exactly the same questions, but there'll be some similarities between those questions.
The more exercise u do, u 'll b exposed to different type of questions. If u r lucky enough, some of the questions might come out in SPM. For me, in paper 1, u should'nt do more than 5 mistakes. Which mean u must get at least 45/50.
Wow..it sounds impossible to some of u ..but trust me it can be done. Apa yang susah sangat, the answers are there, just choose the right one :). The problem is,most of u did lots of careless mistakes. Some dint read the questions carefully especially if they ask either true or false answers.

Another typical careless mistakes can occur in calculation type of questions. In doing calculation, my advice is.. dont simply baca soalan & suddenly press your calculator 'macam nak main game PSP'.Then u think u've got the answer, unfortunately it was the wrong one. WHy?Bcoz most of u dindt convert the units into S.I units. In SPM those 'correct' answer that u've calculated will always appear among the a,b,c & d..So please watch out the trap !

One more thing, if necessary.. please underline important words or phrase. For example,if the question asked for TRUE or FALSE answer, underline those words (false/true). This is to remind that u r alert of what being asked.

In life, if u have more experience, u'll be a wiser person. So as a conclusion, u need to do more exercises, not only for physics but other subjects as well. The more mistakes u made, the more u will learn from it...BUT..dont repeat the same mistakes. I repeat it again..DONT repeat the same mistakes.
I think thats it for today, i wish u all the best in your study..

Electromagnet Application

Ok b4 we move further to next discussion, i just wanna share with u tis video..its another magical world of magnet..

it is called the magnetic levitation theorem of Earnshaw. Dont worrry, u wont be learning this in SPM.
If u r interested in electrical/electronics engineering course..than u've the chance to dig it deeper..

lets get back to business..the next thing u need to know is
To describe the application of electromagnets such as:
1. Door bell
2. Magnetic Relay circuit
3. Speakers
4. Microphone

All these applications can be asked in paper 2( section A / B / C)., especially in essay section.
U can refer your reference book, or from the electromagnet note , pg 4 as provided in this blog. U must understand how does each device works.

SPM 3.1: How to draw Magnetic field Pattern?

Lets continue our discussion, the next objectives u must to know how to draw the :

i. magnetic field pattern due to current in a straight wire. ( How?)
- its simple, just follow a rule called Right Hand Thumb Rule
Look at both of this figure 3.12;

figure 3.12

We can also represent the line of magnetic fields in straight wire as shown in figure 3.13

figure 3.13

ii. Then u must know to draw magnetic field pattern in a coil
..to draw this check yr txt book or any reference book on the diagram. This kind of questions dah lama tak keluar SPM. The pattern should look like in the figure below. Ask your cikgu sekolah or tuition to teach u drawing this.
Things to be observed;
-What happen to the pattern if we reverse the batttery terminal?
- What happen if we increase amount of curent??


iii. U must Learn how to draw magnetic field pattern in a solenoid
This is another important field pattern to draw, it seems to be famous in trial or SPM exam.

How to make an Electromagnet?

Chapter 3 is a very interesting topic, trust me.. u can create so many cool stuff using magnet.
Magnetic field is something mysterious.. some magician used the concept to trick everyone.
U can also try some interesting stuff.. Just look at this video ,

In electromagnet, there's only few calculation and formula involved. Therefore u must really understand the concept. However there's lots of important Rules & Law which need to be fully understood. Please dont try to memorise everything without knowing the real story

3.1: Analysing the Magnetic of Current Carrying Conductor

1. First, u must be able to state what an electromagnet is??

An electromagnet is a temporary magnet produced on iron core when a coil of wire is wrapped around it. Current is supplied along the wire which then produces magnetic field. The iron become magnetized temporarily.

Look at video 3.1. This short video helps you understand how electromagnets turn electricity into magnetism.

Video 3.1

Physics Notes: Eletromagnet

Basically,i've finished discussing Electricity. If u have further questions, u can use the chat box or email me at fizbro @ gmail . com. Perhaps one day i shud setup a forum to discuss more complicated questions.

The next chapter will be Electromagnet, b4 we move on, i need to remind u on certain important things.
By now u must always get use yourself to the formula that will be given in the exam. Everytime u do your own revision or exercise, u must keep the formula booklet next to you.
Please identify which formulae are given and not given. Definitely, U need to memorise those which r not given .

Ok, for the beginning of this chaper 3,i attached a complete notes on ELECTROMAGNET. U need mozilla firefox to view it directly.

Click here to download the file.

Funny Physics Stuff

Hi guys, today i wanna share with u this video. I found it funny, but i warn some of u might found it annoying . So no offense ya.. its just to relax your mind, kalau tak stress pulak.
BTW There's some physics stuff behind it..Enjoy watching :)

SPM Question: Are u efficient enough???

Now its already 7 April and we're moving towards the end of chapter 2. What surprises me that, some of my tuition student said they havent started chapter 2 yet, and still learning Wave.

Wow! I told them u guys need to be prepared, i'm sure b4 your trial, your teacher might ask u to learn certain things on your own. I do not know about u guys, hopefully all of u have almost finished chapter 2.

Ok, lets finish our discussion, in last 3 outcome of chapter 2,
i. u must be able to compare power rating & energy consumption of various electrical appliances
( e.g aircond, cattle, heater etc)

ii. u must also compare various electrical appliances in terms of efficient use of energy.
Here u must know how to calculate efficiency of an electrical appliance
Calculating efficency is to find the percentage; By formula,

Efficiency= (Output/input) x 100

Lets do some analogy,
Just look at your physics result in exam, how efficient r u in studying physics?
For example in paper 1 u r given an input of 50 questions. Out of that 50, you got 30 correct answers. U've wasted 20 questions. So applying efficiency formula,
your Input =50
your Output= 30
Thus your efficiency = (30/50) x 100
= 60%
Well if that is your efficiency in paper 1, i think u need to do lots of EXTRA work :) U r not efficient enough. Where does the 40% go? Is it lost in the middle of your subconscious mind?
If u want to b efficient u shud get 90% & above :)

The same thing goes to eletrical appliances, usually there'll be an input power or energy being supplied. From that input, some of the enery will be used, and some will be lost. The energy being used is the output.
Thus, we can measure its efficiency by applying the formula discussed earlier.

I leave u guys with this comparison between 2 different electrical appliances.

SPM Questions : Electrical Energy

1. Diagram 26 shows an electric circuit. The reading of the ammeter is 0.2 A
and the reading of the voltmeter is 2.8 V

Calculate the electrical energy released by the bulb in 2 minutes.
A 0.56 J B. 1.12J C. 67.20J D. 28.00 J E. 1680.00 J

Apply formula E = V I t , but don’t forget to change time into second
E = 2.8 x 0.2 x ( 2 x 60) = 67.2 J

2. Paper 2 :SPM 04

(a) Namakan satu bahan yang sesuai digunakan sebagai unsur pemanas dalam

pemanas rendam itu. [1 markah] Tungsten

(b) Pemanas rendam itu disambungkan kepada bekalan 240 V. Hitungkan;

(i) arus yang melalui pemanas rendam itu, [2 markah]
P = V x I
1000 = 240 x I
1000/240 = I ,
Thus I = 4.17 A

(ii) rintangan pemanas rendam itu. [2 markah]

V = I x R
R = V/ I
= 240 / 4.17
= 57.55 ohm

(i) State the energy change that occurs when the immersion heater switched on. [1 mark]

Electrical energy is converted to heat energy

(ii) Calculate the energy supplied by each of the immersion heaters P, Q and R to start boiling the water. [4 marks]

In this question, u need to calculate all the energy; use formula E= V I t but please convert the time to second.

• heater P: E = 240 x 6 x ( 8 x 6o) = 691200 J

• heater Q: E = 240 x 5 x (10 x 60) = 720000 J

• heater R: E = 240 x 4 x (9 x 60) = 518400 J

  
  

(iii) Using your answer in (c)(ii), suggest which immersion heater is the most suitable to
heat water. Give one reason for your answer. [2 marks ]

Clue, choose a heater with less energy consumption & time efficient. Most appropriate answer is heater R coz it uses lowest energy.

Electrical Energy & Power

SPM: Intro to Electrical Energy

In this subtopic, u need to recall all the formulas in chp 2 frm 4, energy & power.
Please recall back what does it mean by conservation of energy, otherwise u gonna be lost…trust me this is a MUST.

Ok , now u must appreciate that energy can be transformed. In a battery, chemical energy is stored. When we connect it to a complete circuit, electrical charge(electron) will flow, which then produce current. At this point, chemical energy is converted to electrical enery. Let say in that cicrcuit, u have a bulb, then some of the electrical energy will b transformed into light & heat energy. All these transformation of energy applies the basic principle of conservation of energy.

That’s y i remind u again, it's important to revise chapter 2 form4.
For this reason i leave u with this video..

SPM Questions P3: Emf Graph

SPM03/P3

The graph V agains I above shows the results of the experiment to determine the electromotive force, E, and the internal resistance, r, of a dry cell.

(a) Based on the graph in Figure 8,

(i) what happen when I increases? [1 mark]

voltage decrease

(ii) determine the value of the potential difference, V when the current, I = 0.0 A.

Show on the graph, how you determine V. [2 marks]

(enlarge the graph to see the answer)

(iii) name the physical quantity that represents the value in (a)(ii). [1 mark]

e.m.f

(b) The internal resistance, r, of the dry cell is given by

r = - m

where m is the gradient of the graph. Calculate the value of r. [3 marks]

use yr maths skill to find gradient, at the same time show the line of connected points on the graph

(c) (i) From the graph, state the value of V when I = 0.80 A. Show on the graph how you determine the value of V. [2 mark]

For this question, just show line connecting from 0.8A until touches the graph,

then state the equivalent voltage

(ii) The resistance R is given by R = V/I.

Calculate R when I = 0.80 A. [2 marks]

this is just mathematical, use whatever reading of V u've obtained from the graph from question (c)

(d) State one precaution that should be taken during this experiment. [1 mark]

- make sure all the wires are well connected with the ammeter & voltmeter

- avoid parallax error while taking the reading