iGCSE Physics (0625) 4.1 Simple phenomena of magnetism-Exam Style Questions- New Syllabus
▶️ Answer/Explanation
Detailed solution:
The strength of a magnetic field is indicated by the density or spacing of the magnetic field lines. Inside the solenoid at position $Y$, the field lines are straight, parallel, and very close together, representing a strong and uniform magnetic field. As we move to positions $X$ and $Z$ at the ends of the solenoid, the field lines begin to diverge and spread out into the surrounding space. This increased spacing indicates that the magnetic field strength decreases significantly outside the coils compared to the center. Graph $C$ correctly illustrates this by showing a high, flat peak at $Y$ and lower values at $X$ and $Z$.
▶️ Answer/Explanation
Detailed solution:
Statement $1$ is correct because steel is a hard magnetic material used to make permanent magnets as it retains magnetism well. Statement $2$ is correct as electromagnets consist of a coil around a soft iron core, which only acts as a magnet when an electric current $I$ flows, making them temporary. Statement $3$ is correct because a process called magnetic induction allows a permanent magnet to align the magnetic domains in a nearby unmagnetised iron bar. Since all three statements are scientifically accurate according to the syllabus, the correct choice is $1, 2 \text{ and } 3$.
▶️ Answer/Explanation
Detailed solution:
The strength of a magnetic field is visually represented by the density or spacing of the magnetic field lines.
At position $R$, there are no field lines shown, indicating a neutral point where the opposing fields cancel out, making it the weakest.
At position $Q$, the lines are present but widely spaced, representing a moderate field strength.
At position $P$, the field lines are most concentrated near the pole of the magnet, indicating the strongest field.
Therefore, the correct order from weakest to strongest is $R \rightarrow Q \rightarrow P$, which corresponds to Option D.