NEWTONINE
THE IB PHYSICS LAB
Magnetic field lines go from north to south outside a magnet. Arrows show direction. Closer lines = stronger field.
Electromagnet: a solenoid (coil of wire) with a current; strength increased by adding an iron core, increasing current, or adding more turns. Past papers often ask for ways to increase the strength and applications like electric bells, relays, and loudspeakers.
Draw field lines that never cross.
To remember the right‑hand grip rule for a solenoid: fingers curl in the direction of current, thumb points to the N pole.
In ‘suggest’ questions, always link increased magnetic field to a clear outcome (e.g., ‘stronger electromagnet can lift heavier objects’).
When a current‑carrying wire is placed in a magnetic field, it experiences a force (the motor effect). Direction given by Fleming’s left‑hand rule: thuMb = Motion, First finger = Field, seCond finger = Current.
Electromagnetic induction: when a magnet is moved into a coil, a voltage is induced. The induced voltage increases if the magnet moves faster, the coil has more turns, or the magnet is stronger. This is the basis of generators and transformers.
Past paper questions often show a diagram of a loudspeaker or a simple motor and ask you to explain how it works using the motor effect.
Force on the wire is maximum when the wire is perpendicular to the field; zero when parallel.
For induction, always mention ‘change in magnetic field’ – if the magnet is stationary, no voltage is induced.
Transformers only work with AC because a changing magnetic field is required.
Q1. Which of the following will increase the strength of an electromagnet?
Q2. What rule is used to determine the direction of the force on a current‑carrying conductor in a magnetic field?
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