Solenoid & Electromagnet

• Solenoid — coil of many turns; field like bar magnet.
• Electromagnet — soft iron core inside solenoid; magnet only when current flows.
• Force on current-carrying conductor in magnetic field — Fleming's left-hand rule.
• Motor effect — basis of electric motor (brief).
• Factors increasing field: more turns, higher current, iron core.

1. Solenoid — long coil; uniform field inside; N and S poles at ends.
2. Right-hand grip rule — fingers curl with current; thumb points to N pole.
3. Electromagnet — temporary; used in crane, bell, MRI (intro), relay.
4. Soft iron core — increases field strength; loses magnetism when current off.
5. Fleming's left-hand rule — First finger = Field, seCond = Current, thuMb = Motion.
6. Force on wire — F = BIL sin θ (qualitative at Class 10).
7. Motor — split ring commutator reverses current every half turn.
8. Strength factors — turn count, current, core material.
9. Permanent vs electromagnet — steel retains magnetism; soft iron temporary.
10. NCERT diagram — field lines through solenoid parallel inside.

Predict force direction on wire carrying current into page in uniform B leftward

Step 1 — Field B points left (first finger left).
Step 2 — Current into page (second finger into page).
Step 3 — Thumb points upward → force on wire upward.
Step 4 — Used in DC motor: force rotates coil.
Conclusion: force perpendicular to both B and I (Fleming left-hand rule).

• Using right-hand rule for force (need left-hand for motor effect).
• Misconception: electromagnet works without current.
• Confusing solenoid with toroid field pattern.
• Forgetting soft iron vs steel for temporary magnet.
• Mixing Fleming left (motor) and right (generator) rules.

• What is a solenoid? How is it like a bar magnet?
• State Fleming's left-hand rule.
• Name two uses of electromagnet.
• How can you increase strength of electromagnet?

Open the Practice tab for graded questions on Solenoid & Electromagnet.