Chapter 4 (Electric and magnetic fields) Flashcards
(15 cards)
Define an Electric charge
A property of an object allowing it to generate and experience an electric field.
Define the term “Point charge.”
The part of a particle that generates an electric field and that can experience an electric field as well.
Describe what an electric field is.
A region of space that shows the direction of an electric force that a positively charged particle would experience due to the electric field strength of a point charge.
Define a “Magnetic field.”
A field that arises due to the movement of charge. So, an object is classified as a magnet if there is a constant movement of charge within the material that causes it to generate a magnetic field.
Define a permanent magnet
An object with certain material properties allowing it to naturally produce a persistent magnetic field. Here the movement of charges align so that the individual magnetic fields of each charge sum to form a greater magnetic field.
Define an electromagnet
A magnet is created when moving charges in the form of an electric current occur in a material due to a provided voltage.
Describe how to find the direction of a magnetic field around a current carrying wire
Right-hand grip rule:
Thumb: Direction of current
Curled grip: Direction of magnetic field around wire.
Describe how to find the direction of a magnetic field around a current carrying loop
Describe how to find the direction of a magnetic field around a Solenoid.
Right-hand coil rule:
Thumb: Direction of the magnetic field through each coil
Curled grip: Direction of current through the current-carrying wire.
When is a permanent magnet Static and Changing
Static: Provided the magnet is stationary.
Changing: Provided the magnet is in motion.
When is an electromagnet Static and Changing?
Static: Provided there is a constant current and the magnet is stationary.
Changing: Provided the current is not constant or the electromagnet is in a state of motion.
How is the direction of a magnetic force on a charged particle found
Right hand slap rule
Thumb: Direction of particle’s motion
Fingers: Direction of the magnetic field
Palm slap: Direction of the magnetic force on a positively charged particle.
Backhand slap: Direction of a magnetic force on a negatively charged particle.
What is a DC motor?
Explain its composition
A DC motor is essentially a device that converts electrical potential energy into kinetic energy using the magnetic field acting on a rotating coil of wire.
: A DC power supply
: A split ring commutator or a Slip ring
: A rotating coil of wire
: A magnetic field
: Brushes
Describe the operation and purpose of a split ring commutator
This reverses the electrical connection between the rotating coil of wire and the external circuit every half rotation, changing the direction of current within the coil of wire and reversing the direction of the magnetic forces on each side of the coil experiencing the field.
This ensures the coil of wire rotates in a constant direction at all times.
Describe the operation of a slip ring and outline its effect on the DC motor’s operation
Slip rings ensure there is a constant connection between the external circuit and the rotating coil of wire. If they are used, the direction of current within the coils is not reversed every half rotation and nor is the direction of the magnetic forces on each side of the coil. Thus, the coil will oscillate about its vertical position and eventually come to rest.
