The grade 11 presentation on electromagnetism

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10. Electromagnetism
Physics
Grade 11

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Introduction
Electromagnetism is the study of the properties and relationship between electric currents and
magnetism.
A current-carrying conductor will produce a magnetic field around the conductor.

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Magnetic field around a current carrying conductor

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The Right Hand Rule
The Right Hand Rule says that the magnetic field lines produced by a current-carrying wire
will be oriented in the same direction as the curled fingers of a person’s right hand (in the
“hitchhiking” position), with the thumb pointing in the direction of the current flow.

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Magnetic field around a current carrying loop

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Magnetic field around a solenoid
If we now add another loop with the current in the same direction, then the magnetic field
around each loop can be added together to create a stronger magnetic field. A coil of many
such loops is called a solenoid. A solenoid is a cylindrical coil of wire acting as a magnet
when an electric current flows through the wire.

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Magnetic flux
The magnetic flux through a surface is the product of the component of the magnetic field
normal to the surface and the surface area:
Where:
θ = the angle between the magnetic field, B, and the normal to the loop of area A
A = the area of the loop
B = the magnetic field
The SI unit of magnetic flux is the weber (Wb)
φ=BA cosθ

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Electromagnetic induction
Electromagnetic induction occurs when a changing magnetic field induces a voltage in a
current-carrying conductor.
The magnitude of the induced emf is given by Faraday’s law of electromagnetic Induction:
where φ = B·A and B is the strength of the magnetic field. N is the number of circuit loops. A
magnetic field is measured in units of teslas (T). The minus sign indicates direction and that
the induced emf tends to oppose the change in the magnetic flux. The minus sign can be
ignored when calculating magnitudes.
ℇ=−N
Δ φ
Δt

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