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Magnetic Field of a Current
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Magnetic Field of a Current
Electric current makes a magnetic field around a wire.
More current usually means a stronger magnetic field.
Recommended for Class 10
Magnetic Field of a Current
When electric current flows through a conductor, it produces a magnetic field around the conductor. This shows that electricity and magnetism are closely related.
For a straight current-carrying wire, the magnetic field lines form concentric circles around the wire.
Direction of the Magnetic Field
The direction can be found using the right-hand grip rule.
Point the thumb of your right hand in the direction of conventional current. The curled fingers show the direction of the magnetic field around the wire.
Field Strength
The magnetic field becomes stronger when:
current increases; the distance from the wire decreases.
For a long straight conductor, the field strength is approximately:
**B = μ₀I / 2πr**
where:
`B` = magnetic flux density `I` = current `r` = distance from the wire `μ₀` = permeability of free space
Solenoid
A coil containing many turns of wire is called a solenoid.
When current flows through a solenoid, its magnetic field resembles that of a bar magnet.
The field inside a long solenoid is relatively strong and nearly uniform.
Strengthening an Electromagnet
An electromagnet can be made stronger by:
increasing current; increasing number of turns; * adding a soft-iron core.
Magnetic Field of a Current — Advanced
The magnetic field around a long straight conductor follows an inverse-distance relation, while coils concentrate the field and can produce approximately uniform internal fields.
Common Mistakes
Common Mistakes
- Mistake
Current itself is not a magnetic field; current produces the field.
- Mistake
Do not use the left-hand rule for finding the field around a straight wire.
Revision Zone
60-Second Revision
Quick cues from this topic — use them for last-minute revision.
Current → magnetic field.
Straight wire → circular field lines.
Right-hand grip rule → field direction.
More current → stronger field.
- Definition
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Practice
PQ
Q1. What happens when current passes through a wire?
PQ
Q2. Describe field lines around a straight wire.
PQ
Q3. State the right-hand grip rule.
PQ
Q4. Give two ways to strengthen an electromagnet.
PQ
Q5. What is the role of a soft-iron core?
Exam Practice
EQ
Q1. Explain the magnetic field around a current-carrying wire.
EQ
Q2. State the right-hand grip rule.
EQ
Q3. Explain how field strength changes with current and distance.
EQ
Q4. Describe the field of a solenoid.
EQ
Q5. State three ways to make an electromagnet stronger. ---
School-standard facts for Matric and Intermediate. Original explanations — not copied from textbooks.