Magnetism: Exploring Magnetic Fields, Forces, and Applications in A-Level Science
What Is Magnetism?
Magnetism is a force exerted by magnets and moving charges, producing magnetic fields.
Magnetic Fields (BBB)
A magnetic field is a region where magnetic forces act on moving charges or other magnets.
Unit: Tesla (TTT).
Magnetic Force (FFF)
Force on a Moving Charge
F=qvBsinθF = qvB \sin\thetaF=qvBsinθ
Where:
- qqq: Charge (CCC).
- vvv: Velocity (m/sm/sm/s).
- BBB: Magnetic field (TTT).
- θ\thetaθ: Angle between velocity and field.
Force on a Current-Carrying Wire
F=BILsinθF = BIL \sin\thetaF=BILsinθ
Where:
- III: Current (AAA).
- LLL: Length of wire in the field (mmm).
Applications of Magnetism
Motors and Generators
Magnetism converts electrical energy to mechanical energy and vice versa.
Magnetic Storage
Data is stored using magnetic properties in hard drives.
Medicine
MRI scans use strong magnetic fields to create detailed body images.
Example Problem
A wire of length 1.5 m1.5 \, \text{m}1.5m carries a current of 5 A5 \, \text{A}5A perpendicular to a magnetic field of 0.3 T0.3 \, \text{T}0.3T. Calculate the force on the wire.
- Formula:
F=BILsinθF = BIL \sin\thetaF=BILsinθ
- Substitute Values:
F=0.3⋅5⋅1.5⋅sin90∘=2.25 NF = 0.3 \cdot 5 \cdot 1.5 \cdot \sin 90^\circ = 2.25 \, \text{N}F=0.3⋅5⋅1.5⋅sin90∘=2.25N
Common Mistakes in Magnetism Calculations
- Forgetting to use the angle (sinθ\sin\thetasinθ) in force calculations.
- Mixing up magnetic field strength and force.
- Neglecting the vector nature of magnetic forces.
Practice Questions
- A 2 C2 \, \text{C}2C charge moves at 4 m/s4 \, \text{m/s}4m/s perpendicular to a 0.2 T0.2 \, \text{T}0.2T magnetic field. Calculate the magnetic force.
- Explain the role of magnetism in electric motors.
- Describe one application of magnetic fields in medical imaging.
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