Magnetism

Magnetism

Poles, field lines, magnetic field of the Earth, and a compass.

CAPS

Grade 10 · Physical Sciences (Physics) · Magnetism

Physics is Physical Sciences Paper 1.

  • The paper

    Grade 10 Paper 1 starts from vectors, motion in one dimension, energy, and electrostatics.

  • Working

    Write the formula as it appears on the data sheet, substitute with units, then the answer with the unit and the direction if it is a vector. A positive direction you chose must be stated when the sign matters.

  • The relation

    N pole of compass → magnetic south of Earth. Earth is a magnet

  • How a marker reads it

    Field lines leave N and enter S. Never let them cross on a sketch.

Paper 1 is 150 marks. The data sheet is allowed. A formula copied wrong cannot be saved by a tidy final number.

Diagram

Worked example

Why does a compass needle point roughly north in Limpopo?

Simplified approach

Earth’s magnetic south pole lies near the geographic North Pole, so the compass N-pole is attracted that way.

Culture note

Herders navigating the Soutpansberg at dusk still trust a compass for the same physics.

Formulas

N pole of compass→magnetic south of Earth

Earth is a magnet

How to hunt the missing letter

Do not start by naming the letters. First hunt the missing one: copy every number you can see (Given). The letter with no number is Missing. The asking word is Find. The formula that still contains that letter is what you Calculate.

How to hunt: (1) Underline every number and its unit — those are Given. (2) Circle the asking word — find, calculate, how far, what is. That word names Find. (3) The letter the asking word names, which has no number yet, is Missing. (4) Write the formula with empty letters. Cross out every given letter. The letter still standing is what you Calculate.

  • N

    north pole of a compass

    How you spot this in the sentence

    When the sentence names the north pole of a compass, that letter is N. Copy the number next to it into Given. If the sentence never names it, N is Missing. The compass needle’s N points toward Earth’s magnetic south (geographic north).

    Example:Unlike poles attract; like poles repel.

Exam tricks you must know

These are the moves markers look for — not shortcuts that skip the method, but the habits that earn the method mark.

  • Field lines never cross, start on +, end on −, density is strength

    How:Before you sketch, write those three rules in the margin. Then draw. Crossing lines is an automatic zero on the sketch mark. Density closer together means a stronger field — say that in words if the question asks “compare”.

    When to use it:Any electrostatic or magnetic field sketch.

  • Name the right-hand rule you used — conventional current, not electron flow

    How:Write: “right-hand rule for (force / field / solenoid / induced current)”. Thumb, fingers, palm — assign each to I, B, F before you lock an answer. Markers want the name of the rule as a reason, not only an arrow.

    When to use it:Motors, generators, force on a conductor, and solenoids.

  • List the five, then pick the equation that still has the missing letter

    How:Write a column: v_i, v_f, a, Δt, Δx. Tick every one that has a number. The unticked letter is Missing. Choose the SUVAT line that does not need a letter you do not have — do not start from the formula you remember first.

    When to use it:Any constant-acceleration question that names times, speeds or distances.

Step 1 / 7

Step A — Read the question twice

Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.

Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.

More worked examples

Board walkthroughs on this topic. Open one, copy the working, then try the next.

Example 1 / 20

Two bar magnets are placed with their north poles facing each other. What happens, and why?

4. Step-by-step working

  1. 01

    Identify the given

    Both poles are north: like poles.

    like
  2. 02

    Apply the law

    Like poles repel.

    repel

How we got there

Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.

Explain in another language · 11

1. What is the question asking?

Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: Two bar magnets are placed with their north poles facing each other. What happens, and why?

Before any working — hunt first

Given

Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.

Missing

After you copy the given, the letter that still has no number is missing. The paper is pointing at: What happens, and why. Circle that word — that is the missing variable.

Find

We are required to find: What happens, and why. Write that as a symbol on the left, with a question mark, before you touch a formula.

Calculate

Write like with empty letters. Cross out every letter that already has a number. Calculate the letter that is still standing — that gives What happens, and why.

In other words — as if you have never seen this before

If you have never seen this before: Like poles repel; unlike poles attract. We will name a method in words, write the formula with no numbers, then substitute one line at a time.

2. What do we already know?

Like poles facing.

3. Which method — and why this one?

Like poles repel; unlike poles attract.

4. Step-by-step working

  1. 01 / 05

    Identify the given

    Both poles are north: like poles.

    like

    Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.

  2. 02 / 05

    Apply the law

    Like poles repel.

    repel

    Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.

  3. 03 / 05

    Step G — Sense-check the size

    Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.

    Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.

  4. 04 / 05

    Step F — Box the answer with its unit

    They repel, because like poles repel.

    Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.

  5. 05 / 05

    Step H — What the marker is looking for

    On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.

    Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.

5. The answer

They repel, because like poles repel.

Copy onto your answer sheet — in this order

Formula: like

Answer: They repel, because like poles repel.

6. Check it like a marker

Do not confuse charges and poles: a north pole is not "positive".

7. A trap first-timers fall into

First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”

Ntsako · fx-991ZA PLUS. Tap to calculate.