MYP Physics Electromagnetic Forces and Induction Notes

What Happens When An Electric Current Flows Through A Wire Placed In A Magnetic Field?

1. When an electric current flows through a wire placed in a magnetic field, the wire experiences a force.
2. This force causes the wire to move sideways rather than along the direction of the current.
3. The force acts without physical contact, showing that magnetic fields can cause effects at a distance.
4. This interaction between a current and a magnetic field is called the motor effect.
5. The motor effect explains how electrical energy can be converted into motion.

Why does the wire experience a force?

1. A current-carrying wire produces its own magnetic field around it.
2. When the wire is placed in an external magnetic field, the two magnetic fields interact.
3. On one side of the wire, the magnetic fields reinforce each other.
4. On the opposite side, the magnetic fields oppose each other.
5. This imbalance in magnetic field strength produces a sideways force on the wire.

Direction of the Force

1. The force acts at right angles to:
   1. The direction of the current
   2. The direction of the magnetic field
2. This means the conductor does not move along the field lines or along the current direction.

Reversing the Force

1. If the direction of the current is reversed, the direction of the force also reverses.
2. If the direction of the magnetic field is reversed, the direction of the force also reverses.
3. Reversing both the current and the magnetic field results in the force acting in the same original direction.

What does Fleming’s Left-Hand Rule explain?

1. Fleming’s left-hand rule is used to predict the direction of the force on a current-carrying conductor.
2. It is a prediction tool, not an explanation of why the force exists.
3. The rule is commonly used in questions involving electric motors.

How does Fleming’s Left-Hand Rule work?

1. Hold the left hand with the thumb, first finger, and second finger at right angles.