18 Electromagnetism

How does a circuit breaker work

When there is excessive current flow, the magnetic field produced by the solenoid is stronger and is strong enough to attract the iron latch. The latch releases the spring, causing the safety bar to move outwards. The circuit is open and no current flows through.

How does an electric doorbell work

The iron armature is attracted to the electromagnet and strikes the gong. The iron armature creates a path with less resistance and stops the current from flowing through the electromagnet. The soft iron core loses its magnetism and the iron armature is no longer attracted to the electromagnet. The spring allows the iron armature to return to its original position.

Magnetic force produced by a current carrying conductor…

Increases when current and magnetic field increase, changes direction when magnetic field, electric field and current changes direction.

What are the requirements for a particle to experience a magnetic force in a magnetic field

It has to be charged and moving. It must not be moving parallel to the magnetic field lines.

How can you determine the direction of a force on a charge

The direction of the force can be determined by Flemings left hand rule, where the thumb represents the direction of the force, index finger represents the direction of magnetic field lines and middle finger represents the direction of current flow.

Describe how a compass is used to plot the magnetic field lines in the card.

Place the compass on the card and mark the end points of the needle on the card. Move the compass so that the needle coincides with one of the marked points and mark out a new point. Repeat for more points and connect the point together to obtain one magnetic field lines. The direction of the compass needle is the direction of the magnetic field. Repeat for varying distances between the compass and the wire.