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Question
Refer to the image below and state how the magnetic field pattern indicates regions where the magnetic field is stronger outside the magnet. What happens to the magnetic field when the current in the circuit is reversed?
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Solution 1
The magnetic field strength is more in the region where the field lines are crowded. This means the field strength is maximum near the poles and it reduces as we go away from the poles. The direction of the magnetic field is also reversed.
Solution 2
The diagram shows a solenoid (a coil of wire) connected to a battery and a switch. The lines drawn around the solenoid represent magnetic field lines generated when current flows through the solenoid.
Identifying Stronger Magnetic Field Regions Outside the Magnet
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The density of magnetic field lines indicates the strength of the magnetic field.
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Where the lines are closer together, the magnetic field is stronger.
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Outside the solenoid, the field lines are more spread out, meaning the magnetic field is weaker there.
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Therefore, inside the solenoid, where the lines are very close and mostly parallel, the field is stronger.
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Outside, the field is weaker, but you can still identify slightly stronger regions just around the ends of the solenoid where the lines begin to spread — these regions are closer to the poles.
Effect of Reversing the Current
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The polarity of the magnetic field also reverses.
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This means the north and south poles of the solenoid switch places.
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As a result, the direction of the magnetic field lines changes — they will now emerge from the other end of the solenoid and return into the opposite end.
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However, the pattern of the magnetic field lines (shape and spread) remains the same.
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