Induced EMF and Lenz’s law
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Intros
Examples
Lessons
- A bar magnet is moving toward a solenoid.
What is the direction of the current through the galvanometer and what is the the direction of the magnetic field produced by thus current at location P inside the solenoid?
- A magnet is moving toward an aluminum ring.
In which way will the current flow in the labelled portion of the ring as the magnet moves towards the ring?- Towards 1
- Towards 2
- Towards 3
- Towards 4
- A coil moves at a constant velocity across a region of magnetic field as shown.
Which of the following best shows the emf vs. time graph for the emf induced in the coil as it moves from 1 to 2?
- A conductor is moved to the right through four magnetic field as shown below. In which case will the largest emf be generated?
- A bar magnet is moved away from a coil as shown. What is the direction of the current through the resistor and polarity of the left end of the coil?
- In which of the following situation would the greatest emf be induced in the coil? All changes occur in the same time interval.
Topic Notes
In this lesson, we will learn:
- A changing magnetic field induces current
- Direction of the induced current depends on the direction of the motion of the magnet with respect to the coil.
- No current is induced if the magnet does not move relative to the coil.
- It is the relative motion between the magnet and coil that counts.
- Lenz’s law
Notes:
Induced EMF
- The purpose of this concept is to produce an electric current from a magnetic field.
- A coil of wire, , is connected to a battery. A magnetic field is produced by the current that flows through the coiled wire and is intensified by the iron core.
- The current in the second coiled wire, , is the result of change in magnetic field. The current is detected by the galvanometer only when switch is closed or opened.
- Constant current in produced constant magnetic field, which produces NO current, but changing the magnetic filed can produce an electric current in coil .
- Such current is called the induced current. Changing magnetic field through coil , produces an electric current in the coil.
Lenz’s law;
A current produced by an induced emf moves in a direction so that its magnetic field opposes the original change in flux.
- Magnet is pushed into the coil
- Magnet is pulled out of the coil
- Stationary magnet
