Magnetism & Electromagnetism
Magnetic fields surround permanent magnets and electric currents. When a current-carrying conductor is placed inside an external magnetic field, the two magnetic fields interact to produce a force on the wire (the motor effect, F = BIL), which drives electric motors and loudspeakers.
- Magnetic Field
- The region around a magnet where a force acts on another magnet or on a magnetic material.
- Electromagnet
- A temporary magnet consisting of a coil of wire with an electric current flowing through it, usually wrapped around an iron core.
- Solenoid
- A cylindrical coil of wire acting as a magnet when carrying electric current.
Magnetism & Electromagnetism: Wave Equation (v = fλ) & Force Vector (F = ma) Simulator
Adjust physical variables on the sliders below to see real-time changes in wave geometry, resultant forces, and acceleration.
F_net = 80 N − 25 N = 55 NAcceleration: a = F_net ÷ m = 55 ÷ 10 = 5.50 m/s²Key Concepts & Exam Definitions (5)
- Magnetic Field
- The region around a magnet where a force acts on another magnet or on a magnetic material.
- Electromagnet
- A temporary magnet consisting of a coil of wire with an electric current flowing through it, usually wrapped around an iron core.
- Solenoid
- A cylindrical coil of wire acting as a magnet when carrying electric current.
- Induced Magnet
- A material that becomes a magnet only when placed in a magnetic field.
- Magnetic Flux Density
- A measure of the strength of a magnetic field, measured in Tesla (T).
Quick-Fire Flashcards (5)
Click any card to check the answer, then mark it as Known to track your progress.
What are the four magnetic materials?
In which direction do magnetic field lines point?
What is a solenoid?
What does the thumb represent in Fleming's Left-Hand Rule?
What formula links force, magnetic flux density, current, and length?
Exam-Style Questions & Mark Schemes (3)
Write or think through your answer first, then click Check Mark Scheme to see the exact points examiners award marks for.
- Q1
A 2m long wire carries a current of 3A at right angles to a magnetic field of 0.5T. Calculate the force on the wire.
Click “Check Mark Scheme” to compare your answer, Force = B × I × l = 0.5 × 3 × 2 = 3 N.
- Q2
Describe how you could plot the magnetic field pattern of a bar magnet.
Click “Check Mark Scheme” to compare your answer, Place a plotting compass near the magnet, mark the direction it points, move the compass so the tail aligns with the dot, and repeat to draw lines. Or use iron filings sprinkled on a piece of paper over the magnet.
- Q3
Explain one advantage of an electromagnet over a permanent magnet in a scrapyard crane.
Click “Check Mark Scheme” to compare your answer, An electromagnet can be turned on and off, allowing the crane to easily drop the scrap metal once it has been moved.
Common Exam Questions (3)
What is the motor effect?
The motor effect occurs when a conductor carrying an electric current is placed in a magnetic field; the magnetic field around the wire interacts with the external magnetic field, exerting a force on both the wire and the magnet.
How can you increase the strength of an electromagnet?
Increase the strength of an electromagnet by increasing the electric current flowing through the coil, adding more turns of wire per unit length of the solenoid, or placing a magnetically soft iron core inside the coil.
What is Fleming's Left-Hand Rule?
Fleming's Left-Hand Rule relates the directions of the magnetic field, current, and force in the motor effect: hold your left thumb, first finger, and second finger mutually perpendicular, where First finger = magnetic Field (N to S), seCond finger = conventional Current (+ to -), and thuMb = Motion (force).
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