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State the laws of electromagnetic induction - Leaving Cert Physics - Question d - 2022
Question d
State the laws of electromagnetic induction. A strong magnet is suspended from the end of a string and oscillates in a plane with a constant amplitude. (i) Describ... show full transcript
Worked Solution & Example Answer:State the laws of electromagnetic induction - Leaving Cert Physics - Question d - 2022
Step 1
State the laws of electromagnetic induction.
Answer
- The induced electromotive force (emf) in a closed circuit is proportional to the rate of change of magnetic flux through the circuit.
- The induced current circulates in a direction that creates a magnetic field opposing the change that produced it (Lenz's Law).
- The expression for induced emf is given by: E = - rac{d\Phi_B}{dt} where ( \Phi_B ) is the magnetic flux.
Step 2
Describe what is observed when a sheet of copper metal is placed under the oscillating magnet. Explain this observation.
Answer
When a sheet of copper metal is placed under the oscillating magnet, the amplitude of oscillations of the magnet decreases. This happens because the oscillating magnet induces eddy currents in the copper sheet. These induced currents create their own magnetic field, which opposes the motion of the magnet due to Lenz's Law. As a result, the energy is dissipated as heat in the copper, leading to a reduction in the magnet's oscillation amplitude.
Step 3
Describe what would be observed if instead of the copper, a sheet of plastic was placed under the oscillating magnet. Explain this observation.
Answer
If a sheet of plastic is placed under the oscillating magnet, the oscillations of the magnet will continue without any significant change. This is because plastic is a non-conductive material that does not allow for the flow of electric currents. Therefore, no induced currents are generated, and hence there are no opposing magnetic fields that would affect the magnet's motion. As a result, the magnet will behave as if it is in free space.