Concept Notes (Deep Explanation + Examples)
Introduction
When an electric current flows through a conductor, it produces a magnetic field around it. This phenomenon is called the Magnetic Effects of Current.
This topic is very important for ECET 2026, as questions are frequently asked from rules, force on conductor, Fleming’s rules, and applications.
1️⃣ Discovery of Magnetic Effect of Current
In 1820, Oersted observed that a compass needle deflects when current flows through a nearby wire.
👉 Conclusion:
Electric current produces a magnetic field.
Classroom Example:
When you connect a straight wire to a battery and place a compass near it, the compass needle moves — proving the presence of a magnetic field.
2️⃣ Magnetic Field Around a Straight Current-Carrying Conductor
- The magnetic field lines are concentric circles around the wire.
- Direction depends on the direction of current.
Right-Hand Thumb Rule
- Hold the conductor with your right hand
- Thumb → direction of current
- Curled fingers → direction of magnetic field
Exam Point ⭐
Used to find direction of magnetic field
3️⃣ Magnetic Field Around a Circular Loop
- Field is stronger at the center
- Increases with:
- Increase in current
- Increase in number of turns
Real-life Example:
Electric bells and electromagnets use circular coils.
4️⃣ Solenoid
A solenoid is a long coil of wire with many turns.
Properties:
- Magnetic field inside is strong and uniform
- Acts like a bar magnet
- One end → North, other → South
Lab Example:
Solenoids are used in relays, electric bells, and motors.
5️⃣ Force on a Current-Carrying Conductor in Magnetic Field
When a conductor carrying current is placed in a magnetic field, it experiences a force.
👉 Direction of force is given by Fleming’s Left-Hand Rule
Fleming’s Left-Hand Rule
- Forefinger → Magnetic field
- Middle finger → Current
- Thumb → Force (motion)
Application:
This principle is used in DC motors
6️⃣ Mathematical Expression of Force
Force depends on:
- Magnetic field strength
- Current
- Length of conductor
Formula:
For perpendicular placement:
7️⃣ Fleming’s Right-Hand Rule (Generator Rule)
Used to find direction of induced current.
- Thumb → Motion of conductor
- Forefinger → Magnetic field
- Middle finger → Induced current
Application:
Used in electric generators
8️⃣ Biot–Savart Law (ECET Level)
States that magnetic field strength:
- Is directly proportional to current
- Inversely proportional to distance
9️⃣ Applications of Magnetic Effects of Current
- Electric motors
- Loudspeakers
- Electric bells
- Relays
- Circuit breakers
Exam Tip ⭐
Most ECET questions are rule-based + application-based
3️⃣ ⚙️ Formulas (Plain LaTeX Only)
4️⃣ 🔟 MCQs (ECET + GATE Hybrid)
1. The magnetic field around a straight current-carrying conductor is
A) Straight lines
B) Elliptical
C) Concentric circles
D) Random
2. Which rule gives the direction of magnetic field?
A) Fleming’s Left Hand
B) Fleming’s Right Hand
C) Right Hand Thumb Rule
D) Maxwell’s Rule
3. Magnetic field inside a solenoid is
A) Zero
B) Non-uniform
C) Weak
D) Uniform
4. Fleming’s Left-Hand Rule is used in
A) Generator
B) Transformer
C) Motor
D) Rectifier
5. Force on conductor is maximum when angle is
A) 0°
B) 90°
C) 45°
D) 180°
6. Unit of magnetic field is
A) Weber
B) Tesla
C) Ohm
D) Henry
7. Which device works on magnetic effect of current?
A) LED
B) Battery
C) Electric motor
D) Capacitor
8. Direction of induced current is found by
A) Left hand rule
B) Right hand rule
C) Thumb rule
D) Maxwell rule
9. Magnetic field strength increases with
A) Distance
B) Decrease in current
C) Increase in current
D) Zero current
10. Solenoid behaves like
A) Capacitor
B) Resistor
C) Bar magnet
D) Fuse
5️⃣ ✅ Answer Key (WordPress Table — NO HTML)
Q No | Answer
1 | C
2 | C
3 | D
4 | C
5 | B
6 | B
7 | C
8 | B
9 | C
10 | C
6️⃣ 🧠 MCQ Explanations
Q1: Magnetic field lines form concentric circles → C correct
Others are incorrect shapes.
Q2: Right-hand thumb rule gives magnetic field direction → C
Q3: Inside solenoid field is uniform → D
Q4: Motor works on force principle → C
Q5: 
, force is max → B
Q6: SI unit is Tesla → B
Q7: Motor converts electrical to mechanical energy → C
Q8: Generator uses right-hand rule → B
Q9: Field ∝ current → C
Q10: Solenoid acts like bar magnet → C
7️⃣ 🎯 Motivation (ECET 2026 Specific)
This topic appears every year in ECET Physics because it connects theory with machines like motors and generators.
Mastering this topic means you secure easy + sure marks.
Consistency in physics = rank improvement guaranteed 💪
8️⃣ 📲 CTA (Fixed)
Join our ECET 2026 CSE WhatsApp Group for daily quizzes & study notes:
https://chat.whatsapp.com/GniYuv3CYVDKjPWEN086X9
